fix(web): replay cursor movements the way a terminal paints them

Carriage return and backspace only MOVE the cursor; neither erases. Both of
my earlier approximations were wrong, and I checked each case against a real
terminal rather than reasoning about it:

`100%\rOK` shows `OK0%`, not `OK` — the redraw is shorter than the frame
beneath it, so the tail stands. `abc\b` still shows `abc`, not `ab` — a
trailing backspace has nothing to overwrite. `\x1b[31mgone\rkept` paints
`kept` RED, because a carriage return does not reset the graphic state, which
one of my own tests had asserted the opposite of.

Both now replay into a per-line column buffer with SGR state stamped per
column, as a terminal stores it per cell. That gives the partial-overwrite
case its real result too: red `bad`, three backspaces, then `ok` shows `okd`
with the `d` still red, since `ok` reached only two of the three cells.

The presenter description now also renders at every site. An expanded row
draws it itself — the collapsed summary is hidden while open, so otherwise
the description was visible only collapsed, the opposite of "above the card"
— and the details panel draws it above the card as well.

Three of my own tests encoded the wrong semantics and were corrected with
their behavior, and the emit loop's gap-filling arm was removed as
unreachable: `\r` and backspace only move left, so no column can be unwritten.

.agents/notes/implemented/feature/2026-07-28-web-terminal-card.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write .agents/notes/implemented/feature/2026-07-28-web-terminal-card.md
-2026-07-28-web-terminal-card.md: 87cb40331bca6a1bfcdd4e8ecd9bbe69c6572be0
-2026-07-28-web-terminal-card.zh.md: ab5a35d6f76427cf1e0338d8491bd3485cb41302
+2026-07-28-web-terminal-card.md: 284c91cc936c1e757f20f0d0d8afbe4b4c0afc42
+2026-07-28-web-terminal-card.zh.md: 3ffcf232942eed883f44da583c68455715d347ce

.agents/notes/implemented/feature/2026-07-28-web-terminal-card.md

@@ -12,7 +12,7 @@ The Web client ignored it. `packages/client/ui-conversation/src/client/contract/
 
 ## Decision
 
-`TerminalBlock` is a `ui-primitives` component that renders a shell command as a terminal surface, and both Web render sites for a bash call consume the terminal render intent through it: the chat tool row's expanded body and the details panel's Output section. `ui-conversation/src/client/contract/terminal-card-model.ts` is the single place that turns the snapshot's `callView`/`resultView` pair into the component's props, so the two sites cannot disagree about a command, its cwd, or its exit status. It returns null — the generic path — whenever neither side declares `card: 'terminal'`, including a `card` value this client version does not know, and whenever a settled call's result view is generic, which is how the bash tool's execution errors and background starts keep their existing rendering. Two duties the render-intent contract assigns to the UI bridge land here rather than in the tool: a settled result's `title` REPLACES the pending one, and the working directory resolves against the session workspace — an absolute view cwd is used as-is, a relative one joins under the workspace, and an omitted one IS the workspace, which is the common case for a bash call with no `workdir`. A pure presenter cannot see the session cwd, which is why the resolution belongs at this seam; each render site supplies the cwd off the session list row. Only a PRESENT call view can mean "omitted, so use the workspace": when the paging window drops the call head there is no cwd anywhere — the result view carries none — and the original call may have used an explicit workdir, so the prompt draws a bare `$` rather than naming a directory it cannot know. The resolved path also normalizes its `.`/`..` segments, because the bash executor resolves the workdir before running: a `..` against `/w/app` runs in `/w`, so the prompt label has to read `w` rather than `..`. A UNC path's `server` and `share` are part of its root rather than poppable segments, since Windows cannot climb above a share. The call view's `description` rides the same derivation, since the contract renders it above the card and it must outrank the row's args-derived summary.
+`TerminalBlock` is a `ui-primitives` component that renders a shell command as a terminal surface, and both Web render sites for a bash call consume the terminal render intent through it: the chat tool row's expanded body and the details panel's Output section. `ui-conversation/src/client/contract/terminal-card-model.ts` is the single place that turns the snapshot's `callView`/`resultView` pair into the component's props, so the two sites cannot disagree about a command, its cwd, or its exit status. It returns null — the generic path — whenever neither side declares `card: 'terminal'`, including a `card` value this client version does not know, and whenever a settled call's result view is generic, which is how the bash tool's execution errors and background starts keep their existing rendering. Two duties the render-intent contract assigns to the UI bridge land here rather than in the tool: a settled result's `title` REPLACES the pending one, and the working directory resolves against the session workspace — an absolute view cwd is used as-is, a relative one joins under the workspace, and an omitted one IS the workspace, which is the common case for a bash call with no `workdir`. A pure presenter cannot see the session cwd, which is why the resolution belongs at this seam; each render site supplies the cwd off the session list row. Only a PRESENT call view can mean "omitted, so use the workspace": when the paging window drops the call head there is no cwd anywhere — the result view carries none — and the original call may have used an explicit workdir, so the prompt draws a bare `$` rather than naming a directory it cannot know. The resolved path also normalizes its `.`/`..` segments, because the bash executor resolves the workdir before running: a `..` against `/w/app` runs in `/w`, so the prompt label has to read `w` rather than `..`. A UNC path's `server` and `share` are part of its root rather than poppable segments, since Windows cannot climb above a share. The call view's `description` rides the same derivation, since the contract renders it above the card and it must outrank the row's args-derived summary. All three render sites draw it: both chat-row shapes and the details panel. An expanded row draws it itself, because the collapsed summary is hidden while a row is open — without that the description would only ever be visible collapsed, which is the opposite of what "above the card" means.
 
 The component's contract:
 
@@ -20,7 +20,7 @@ The component's contract:
 - **One run-state dot for the call, on the first row.** `StateDot` in three of its four states: the chase while running, red for the exit status that also renders the pill, green for a clean settle — the same indicator a tool row's leading icon uses, so a row and its own card cannot disagree about one command. The dot exists because the first question a reader has about a shell command is whether it is still running, and without it that had to be inferred from the absence of output — which a settled command producing no output also looks like. It sits out of flow in a gutter reserved to the left of the card surface, so it neither indents its command nor depends on the command's own text metrics to line up with it. Exactly one dot, whatever the line count: the exit status the view carries is the whole call's, and bash reports no per-command status, so a dot per line would assert of a line that succeeded inside a failing call that the line itself failed. The single visually hidden text label carries the same scope, since `StateDot` is `aria-hidden` and one label per row would read to assistive technology as several distinct outcomes.
 - **No soft wrapping.** Output lines are `white-space: pre` inside a horizontally scrolling box. Column alignment survives; a long line scrolls instead of folding.
 - **Height cap with an expand control.** Output longer than `DEFAULT_TERMINAL_MAX_LINES` (16) lines shows `ceil(max/2)` head lines plus the remaining tail lines, with a button in between that reports the hidden count and expands. The count is of parsed lines after the trailing output terminator is dropped, so an N-line output ending in a newline is N lines. The split arithmetic is the same as the TUI transcript's collapsed tool card (`packages/ui/tui/src/components/transcript.ts`), so one command's head and tail slices agree between the two front ends.
-- **ANSI color.** `anser` splits the SGR runs; `ui-primitives/src/ansi.ts` resolves each run into an inline style rendered as React spans. A foreground-only run maps the basic 16 colors onto `--dsw-*` theme tokens so authored color stays legible under both themes; a run that paints its own background keeps anser's literal rgb for both so its intended contrast survives, as do 256-palette, truecolor, and the two basic colors this design system has no token for. Sequences that carry no color (OSC strings, non-CSI escapes, inert C0 controls) are stripped before parsing so they never reach the DOM as literal characters. Two cursor movements resolve before that strip, because their effect on the visible text has to land before the characters expressing them are dropped: a carriage return reduces its line to the final redraw, and a backspace overwrites the character before it, so `abc` followed by two backspaces and `XY` reads `aXY` as a terminal draws it. Both are per-line, so neither reaches across a newline. A backspace steps over CSI sequences rather than erasing their bytes: a sequence moves no cursor, and eating part of one would corrupt it and repaint everything after with whatever the mangled remainder parses as, so it walks back to the last PRINTED character and drops that instead — the surviving text keeps the color its run authored.
+- **ANSI color.** `anser` splits the SGR runs; `ui-primitives/src/ansi.ts` resolves each run into an inline style rendered as React spans. A foreground-only run maps the basic 16 colors onto `--dsw-*` theme tokens so authored color stays legible under both themes; a run that paints its own background keeps anser's literal rgb for both so its intended contrast survives, as do 256-palette, truecolor, and the two basic colors this design system has no token for. Sequences that carry no color (OSC strings, non-CSI escapes, inert C0 controls) are stripped before parsing so they never reach the DOM as literal characters. Cursor movements resolve before that strip, into a per-line column buffer rather than by string surgery, because carriage return and backspace only MOVE the cursor — neither erases anything, so what a reader sees is whatever each column last had written to it. `100%` then a carriage return and `OK` shows `OK0%`, since the redraw is shorter than the frame beneath it; a trailing `abc` plus a backspace still shows `abc`, since nothing overwrote the `c`; `abc` plus two backspaces and `XY` shows `aXY`. Each of these was checked against a real terminal, because the earlier truncate-and-delete approximations looked right and were not. SGR state is stamped per column as a terminal stores it per cell, so a partial overwrite keeps each surviving character's own color: red `bad`, three backspaces, then `ok` shows `okd` with the `d` still red. A CSI sequence occupies no column and changes only the state later writes are stamped with, which is also why a carriage return does not reset color.
 - **Exit status and copy.** A non-zero exit code or a signal renders a status pill, matching the exit-status distinction the bash tool's own renderer draws; a clean exit renders none, and settled empty output renders a dimmed placeholder. The copy control copies the raw output text, not the rendered tree, so the prompt line and the pill stay out of the clipboard.
 
 Geometry, radius, and fonts mirror `CodeBlock`, so a terminal card and a fenced code block match visually; `white-space: pre` plus horizontal scroll is the deliberate divergence. The clipboard write both components need moved out of `CodeBlock` into a package-internal `src/clipboard.ts`, unexported so it stays an implementation detail of the two blocks.

.agents/notes/implemented/feature/2026-07-28-web-terminal-card.zh.md

@@ -12,7 +12,7 @@ Web client 却对它视而不见。`packages/client/ui-conversation/src/client/c
 
 ## Decision
 
-`TerminalBlock` 是 `ui-primitives` 中把 shell 命令渲染为终端表面的组件，bash 调用在 Web 侧的两个渲染点都经由它消费 terminal 渲染意图：聊天工具行展开后的正文，以及详情面板的 Output 区。`ui-conversation/src/client/contract/terminal-card-model.ts` 是把快照上的 `callView`/`resultView` 这一对转换为该组件 props 的唯一位置，因此两个渲染点不可能在命令、cwd 或退出状态上产生分歧。当两侧都不声明 `card: 'terminal'` 时它返回 null，即走 generic 路径——包括本 client 版本不认识的 `card` 取值；当一个已落定调用的结果视图是 generic 时同样返回 null，这正是 bash 工具的执行错误与后台启动得以保持既有渲染的方式。渲染意图契约交给 UI 桥接层的两项职责也落在这里，而不在工具侧：已落定结果的 `title` **替换**待定标题；工作目录针对会话 workspace 解析——视图给出的绝对路径原样使用，相对路径在 workspace 之下拼接，省略则**就是** workspace，而这正是不带 `workdir` 的 bash 调用的常见情形。纯 presenter 看不到会话 cwd，因此该解析属于这道接缝；两个渲染点各自从会话列表行取出 cwd 传入。只有**存在**的调用视图才能表示「省略了 cwd，因此取 workspace」：当分页窗口丢掉调用头时，任何地方都不再有 cwd——结果视图并不携带它——而原调用完全可能使用过一个显式 workdir，因此提示行绘制一个裸 `$`，而不是命名一个它无法知晓的目录。解析后的路径还会归一化其 `.`／`..` 段，因为 bash 执行器在运行前就已解析 workdir：相对 `/w/app` 的 `..` 实际运行在 `/w`，因此提示标签必须读作 `w` 而不是 `..`。UNC 路径的 `server` 与 `share` 属于其根，而非可弹出的路径段，因为 Windows 无法越过一个共享向上。调用视图的 `description` 走同一处推导，因为契约把它渲染在卡片上方，且它必须优先于该行由参数推导出的摘要。
+`TerminalBlock` 是 `ui-primitives` 中把 shell 命令渲染为终端表面的组件，bash 调用在 Web 侧的两个渲染点都经由它消费 terminal 渲染意图：聊天工具行展开后的正文，以及详情面板的 Output 区。`ui-conversation/src/client/contract/terminal-card-model.ts` 是把快照上的 `callView`/`resultView` 这一对转换为该组件 props 的唯一位置，因此两个渲染点不可能在命令、cwd 或退出状态上产生分歧。当两侧都不声明 `card: 'terminal'` 时它返回 null，即走 generic 路径——包括本 client 版本不认识的 `card` 取值；当一个已落定调用的结果视图是 generic 时同样返回 null，这正是 bash 工具的执行错误与后台启动得以保持既有渲染的方式。渲染意图契约交给 UI 桥接层的两项职责也落在这里，而不在工具侧：已落定结果的 `title` **替换**待定标题；工作目录针对会话 workspace 解析——视图给出的绝对路径原样使用，相对路径在 workspace 之下拼接，省略则**就是** workspace，而这正是不带 `workdir` 的 bash 调用的常见情形。纯 presenter 看不到会话 cwd，因此该解析属于这道接缝；两个渲染点各自从会话列表行取出 cwd 传入。只有**存在**的调用视图才能表示「省略了 cwd，因此取 workspace」：当分页窗口丢掉调用头时，任何地方都不再有 cwd——结果视图并不携带它——而原调用完全可能使用过一个显式 workdir，因此提示行绘制一个裸 `$`，而不是命名一个它无法知晓的目录。解析后的路径还会归一化其 `.`／`..` 段，因为 bash 执行器在运行前就已解析 workdir：相对 `/w/app` 的 `..` 实际运行在 `/w`，因此提示标签必须读作 `w` 而不是 `..`。UNC 路径的 `server` 与 `share` 属于其根，而非可弹出的路径段，因为 Windows 无法越过一个共享向上。调用视图的 `description` 走同一处推导，因为契约把它渲染在卡片上方，且它必须优先于该行由参数推导出的摘要。三个渲染点都会绘制它：两种聊天行形态与详情面板。展开后的行自行绘制它，因为一行处于展开态时其折叠摘要是隐藏的——否则该描述将只在折叠时可见，这与「位于卡片上方」的含义正好相反。
 
 该组件的契约：
 
@@ -20,7 +20,7 @@ Web client 却对它视而不见。`packages/client/ui-conversation/src/client/c
 - **整次调用一枚运行状态点，位于第一行。** 它是 `StateDot` 四种状态中的三种：运行期间为追逐动画，与渲染状态徽章相同的退出状态为红色，干净落定为绿色——与工具行行首图标使用同一个指示器，因此一行与其自身的卡片不可能对同一条命令产生分歧。该状态点存在的理由是：读者对一条 shell 命令的第一个问题就是它是否仍在运行；没有它时，这一点只能从「没有输出」推断，而一条落定后无输出的命令看起来也一样。它以脱离文档流的方式落在卡片表面左侧预留的落区里，因此既不会缩进其命令，也不依赖命令自身的文本度量来与之对齐。无论有多少行，都只有一枚：视图携带的退出状态属于整次调用，而 bash 不报告逐条命令的状态，因此每行一枚状态点就等于在断言——一条在失败调用中其实成功了的命令行自身失败了。那一处视觉隐藏的文本标签具有相同的作用域，因为 `StateDot` 是 `aria-hidden`，而每行一个标签会被辅助技术读成好几个各自独立的结果。
 - **不软换行。** 输出行使用 `white-space: pre`，置于横向滚动的容器内。列对齐得以保留；长行滚动，而非折行。
 - **高度上限与展开控件。** 输出超过 `DEFAULT_TERMINAL_MAX_LINES`（16）行时，显示 `ceil(max/2)` 行首部加余下的尾部行数，中间是一个按钮，报告被隐藏的行数并可展开。计数针对的是剥除输出末尾终止符之后解析出的行，因此以换行结尾的 N 行输出就是 N 行。切分算法与 TUI transcript 折叠态工具卡片（`packages/ui/tui/src/components/transcript.ts`）完全一致，因此同一条命令的首尾切片在两个前端之间吻合。
-- **ANSI 颜色。** `anser` 切分 SGR 分段；`ui-primitives/src/ansi.ts` 把每段解析为内联样式，渲染成 React span。只设前景色的分段把基本 16 色映射到 `--dsw-*` 主题 token，使作者指定的颜色在两种主题下都可读；自行绘制背景的分段则前后景都保留 anser 给出的字面 rgb，以保住它意图中的对比度，256 色板、truecolor 以及本设计系统没有对应 token 的两种基本色同样如此。不承载颜色的转义序列（OSC 串、非 CSI 转义、无显示意义的 C0 控制符）在解析前被剥除，因此绝不会以字面字符抵达 DOM。两种光标移动在该剥除之前先行结算，因为它们对可见文本的作用必须先落地，之后才能丢弃表达它们的那些字符：回车把所在行归约为最后一次重绘，退格覆盖它前面的字符——于是 `abc` 后接两个退格再接 `XY` 读作 `aXY`，与终端的绘制一致。两者都按行结算，因此都不会跨越换行。退格会跨过 CSI 序列，而不是擦掉它的字节：序列本身不移动光标，吃掉它的一部分会破坏该序列，并让其后的一切按被损坏的残余重新着色，因此退格回退到最后一个**已打印**字符并删除它——存活下来的文本保留其所在分段所声明的颜色。
+- **ANSI 颜色。** `anser` 切分 SGR 分段；`ui-primitives/src/ansi.ts` 把每段解析为内联样式，渲染成 React span。只设前景色的分段把基本 16 色映射到 `--dsw-*` 主题 token，使作者指定的颜色在两种主题下都可读；自行绘制背景的分段则前后景都保留 anser 给出的字面 rgb，以保住它意图中的对比度，256 色板、truecolor 以及本设计系统没有对应 token 的两种基本色同样如此。不承载颜色的转义序列（OSC 串、非 CSI 转义、无显示意义的 C0 控制符）在解析前被剥除，因此绝不会以字面字符抵达 DOM。光标移动在该剥除之前先行结算，且落在逐行的列缓冲里而不是靠字符串手术，因为回车与退格**只移动**光标——两者都不擦除任何东西，所以读者看到的就是每一列最后被写入的内容。`100%` 后接回车再接 `OK` 显示为 `OK0%`，因为这次重绘比它下面的帧更短；末尾 `abc` 加一个退格仍显示 `abc`，因为没有任何东西覆盖过那个 `c`；`abc` 加两个退格再接 `XY` 显示 `aXY`。这些用例都对照真实终端核实过，因为先前「截断加删除」的近似看起来是对的，实际并不对。SGR 状态按列打戳，与终端按单元格存储颜色的方式一致，因此部分覆盖会保留每个存活字符自身的颜色：红色 `bad`、三个退格、再写 `ok`，显示为 `okd` 且那个 `d` 仍是红的。CSI 序列不占列，只改变后续写入被打上的状态——这也正是回车不会重置颜色的原因。
 - **退出状态与复制。** 非零退出码或信号渲染一枚状态徽章，与 bash 工具自身渲染器所作的退出状态区分一致；干净退出不渲染徽章，落定后的空输出渲染一处变暗的占位文字。复制控件复制的是原始输出文本而非渲染后的树，因此提示符行与徽章不会进入剪贴板。
 
 几何尺寸、圆角与字体沿用 `CodeBlock`，因此终端卡片与围栏代码块在视觉上一致；`white-space: pre` 加横向滚动是有意的分歧。两个组件都需要的剪贴板写入从 `CodeBlock` 中提取到包内部的 `src/clipboard.ts`，不对外导出，因此它仍是这两个块的实现细节。