fix(web): address diff card review — split terminator, error arm, wire narrowing

- DiffBlock: an empty side contributes zero lines and a trailing newline is a
  terminator, so a create ending in a newline draws one added line (not a
  phantom empty one) and a full deletion draws no phantom + line.
- diffCardModel: narrow the wire diffs payload (card is the only validated
  field) so a malformed diff card falls back to the generic path instead of
  throwing inside DiffBlock.
- FileMutationRow: surface the result text when an errored mutation has no diff
  card, so a failed edit/write is more than a red dot.
- copyText ends its closed union on assertNever.
- Docs: drop the "bridge relativizes" claim, record the file-count divergence
  from the TUI footer, correct the built-boot overclaim, note why the row title
  outranks the view title, and make fixture turn 67 args self-consistent.
- Tests: terminator/empty-side/interior-blank rows, wire-narrowing null arms,
  the error-text arm and its name/code fallback, stopped state, no-path summary,
  and the registration/disposal shape.

.agents/notes/implemented/feature/2026-07-30-web-diff-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/2026-07-30-web-diff-card.md
-2026-07-30-web-diff-card.md: 5e43d5d29f7f4000efebc166724ec9d921d2b441
-2026-07-30-web-diff-card.zh.md: aac577cfa8dd9e0bf5f17a729d049d207a64d374
+2026-07-30-web-diff-card.md: 8087ce698e65f78c7c6f51211ef00e3b0ab58ed9
+2026-07-30-web-diff-card.zh.md: d85ac1f2e13c7fb3732b327b40122076337ac538

.agents/notes/implemented/feature/2026-07-30-web-diff-card.md

@@ -16,9 +16,9 @@ This is the [terminal card](2026-07-28-web-terminal-card.md) done for the `diff`
 
 `DiffBlock` is a `ui-primitives` component that renders a file mutation as an inline diff surface, and both Web render sites for a write/edit call consume the diff render intent through it: the chat tool row's body and the details panel's Output section. `ui-conversation/src/client/contract/diff-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 change. It returns null — the generic path — whenever neither side declares `card: 'diff'`, including a `card` value this client version does not know, and whenever a settled call's result view is generic, which is how write/edit keep their execution errors on the generic path. The result side is authoritative once the call settles: the applied hunks replace the call-time diff derived from the arguments alone. A paging window that drops the call head still renders, because the result view carries the whole change.
 
-The component's contract mirrors the TUI's `diffLines` (`packages/ui/tui/src/components/transcript.ts`) so a diff reads the same across front ends:
+The component's contract follows the TUI's `diffLines` (`packages/ui/tui/src/components/transcript.ts`) so a diff reads the same shape across front ends, with one deliberate divergence noted below (the file count):
 
-- **One path header per file.** A new file opens a bold path header; a same-file second hunk (a scattered edit, or a `replace_all`) opens with a `⋯` gap instead of repeating the path. The `N file(s)` footer counts distinct paths.
+- **One path header per file.** A new file opens a bold path header; a same-file second hunk (a scattered edit, or a `replace_all`) opens with a `⋯` gap instead of repeating the path. The `N file(s)` footer counts DISTINCT paths — the divergence from the TUI, whose footer uses `diffs.length` and so reads two hunks in one file as `2 files` where this reads `1 file`.
 - **The change in the diff's own colors.** A removed line is `- ` on the error token, an added line is `+ ` on the success token, drawn verbatim with `white-space: pre` inside a horizontally scrolling box — a source line is read by its indentation, so it scrolls rather than folds. A create (`oldText: null`) has no removed side.
 - **Height cap with an expand control.** A diff longer than `DEFAULT_DIFF_MAX_LINES` (16) shows `ceil(max/2)` head rows plus the remaining tail rows, with a button between reporting the hidden count. The split arithmetic matches `TerminalBlock` and the TUI's collapsed card, so a long diff's head and tail slices agree across front ends.
 - **Footer and copy.** A dim `└ +A -R · N file(s)` footer summarizes the change; `+A -R` are the added/removed line counts, the same per-side counts the TUI footer draws. The copy control copies the prefixed diff text (path headers, `- `/`+ ` lines, the `⋯` gap), so a multi-file copy stays attributable.
@@ -47,7 +47,7 @@ The multi-file arm of `DiffBlock` (one card, several path headers) has no produc
 
 `packages/client/ui-conversation/tests/diff-card.spec.tsx` pins the wiring at every render site: `diffCardModel`'s derivation and each of its null arms, the result hunks replacing the call-time diff, a window-truncated call still rendering from the result, the chat row's diff body, `FileMutationRow`'s resident card and its path link opening cwd-resolved through the host, its registration under both `write` and `edit`, and the panel's Output section.
 
-The fixture (`packages/client/connection/src/client/fixture.ts`) carries three diff turns so the built-boot snapshot pins all three arms at both render sites: a single-hunk edit (turn 62, keyed `FileMutationRow`), a create/write (turn 63), and a multi-hunk edit (turn 67, the `⋯` gap between two scattered hunks in one file).
+The fixture (`packages/client/connection/src/client/fixture.ts`) carries three diff turns so a `?fixture` server and the per-package wiring suite exercise all three arms at both render sites: a single-hunk edit (turn 62, keyed `FileMutationRow`), a create/write (turn 63), and a multi-hunk edit (turn 67, the `⋯` gap between two scattered hunks in one file). The built-boot snapshot (`apps/web/tests/built-boot.snapshot.ts`) is a boot-assembly smoke that asserts only that the graph mounts and reaches chat content (`data-sample="bash-global"`); by its own contract it carries no diff-behavior assertions, which the wiring suite owns.
 
 ## Related
 

.agents/notes/implemented/feature/2026-07-30-web-diff-card.zh.md

@@ -16,9 +16,9 @@ Web 客户端忽略了它。write/edit 调用落到 `GenericToolCard`，其行
 
 `DiffBlock` 是一个 `ui-primitives` 组件，把文件改动渲染为内联 diff 表面，write/edit 调用的两个 Web 渲染点都通过它消费 diff 渲染意图：chat 工具行的行体和详情面板的 Output 区。`ui-conversation/src/client/contract/diff-card-model.ts` 是唯一把快照的 `callView`/`resultView` 对转成组件 props 的地方，因此两个渲染点不会对一次改动产生分歧。当两侧都未声明 `card: 'diff'` 时它返回 null —— 走通用路径 —— 包括本客户端版本不认识的 `card` 值，以及已结算调用的 result view 是 generic 的情况（write/edit 的执行错误正是这样留在通用路径上的）。调用结算后 result 侧是权威：已应用的 hunk 替换仅从参数推导的 call 时 diff。分页窗口丢弃了 call 头也仍能渲染，因为 result view 携带完整改动。
 
-组件的契约镜像 TUI 的 `diffLines`（`packages/ui/tui/src/components/transcript.ts`），使 diff 在两个前端读起来一致：
+组件的契约遵循 TUI 的 `diffLines`（`packages/ui/tui/src/components/transcript.ts`），使 diff 在两个前端读起来是同一形态，仅文件计数一处刻意分歧（见下）：
 
-- **每个文件一个路径头。** 新文件开启一个粗体路径头；同文件的第二个 hunk（分散编辑，或 `replace_all`）以一个 `⋯` gap 开启，而非重复路径。`N file(s)` 页脚统计去重后的路径数。
+- **每个文件一个路径头。** 新文件开启一个粗体路径头；同文件的第二个 hunk（分散编辑，或 `replace_all`）以一个 `⋯` gap 开启，而非重复路径。`N file(s)` 页脚统计**去重后的路径数** —— 这是与 TUI 的分歧:TUI 页脚用 `diffs.length`，同文件两个 hunk 在那里读作 `2 files`，此处读作 `1 file`。
 - **改动用 diff 自身的颜色。** 删除行是 error token 上的 `- `，新增行是 success token 上的 `+ `，在横向滚动的盒子里以 `white-space: pre` 逐字绘制 —— 源码行靠缩进阅读，所以滚动而不折行。新建（`oldText: null`）没有删除侧。
 - **高度上限带展开控件。** 长于 `DEFAULT_DIFF_MAX_LINES`（16）的 diff 显示 `ceil(max/2)` 个头部行加剩余尾部行，中间一个按钮报告隐藏行数。分割算术与 `TerminalBlock` 和 TUI 的折叠卡片一致，因此长 diff 的头尾切片在两个前端一致。
 - **页脚与复制。** 暗色 `└ +A -R · N file(s)` 页脚概括改动；`+A -R` 是新增/删除行数，与 TUI 页脚绘制的每侧计数相同。复制控件复制带前缀的 diff 文本（路径头、`- `/`+ ` 行、`⋯` gap），使多文件复制保持可归属。
@@ -47,7 +47,7 @@ chat 行把 diff 常驻渲染在路径链接摘要之下，上限 `CHAT_DIFF_MAX
 
 `packages/client/ui-conversation/tests/diff-card.spec.tsx` 钉住每个渲染点的接线：`diffCardModel` 的派生及其每个 null 支路、result hunk 替换 call 时 diff、窗口截断的 call 仍从 result 渲染、chat 行的 diff 体、`FileMutationRow` 的常驻卡片及其路径链接经 host 以 cwd 解析打开、其在 `write` 与 `edit` 下的注册、以及面板的 Output 区。
 
-fixture（`packages/client/connection/src/client/fixture.ts`）携带三个 diff turn，使 built-boot snapshot 在两个渲染点钉住全部三个支路：单 hunk 编辑（turn 62，keyed `FileMutationRow`）、新建/写入（turn 63）、多 hunk 编辑（turn 67，一个文件内两处分散 hunk 之间的 `⋯` gap）。
+fixture（`packages/client/connection/src/client/fixture.ts`）携带三个 diff turn，使 `?fixture` 服务与 per-package 接线测试套件在两个渲染点演练全部三个支路：单 hunk 编辑（turn 62，keyed `FileMutationRow`）、新建/写入（turn 63）、多 hunk 编辑（turn 67，一个文件内两处分散 hunk 之间的 `⋯` gap）。built-boot snapshot（`apps/web/tests/built-boot.snapshot.ts`）是启动装配 smoke，只断言图挂载并抵达 chat 内容（`data-sample="bash-global"`）；按其自身契约它不带 diff 行为断言，那由接线套件负责。
 
 ## Related