feat(gui): animate sidebar collapse and grow the rail control set

The collapsed rail becomes a 56px icon column (24px controls between 16px
paddings) carrying expand, new session, search, and new workspace — each
aligned with its expanded counterpart; rail search expands the sidebar and
focuses the search box. Collapse/expand now animates: the frame transitions
grid-template-columns (and the surviving handle its left) on the deepsuite
sider curve — --ds-ease-in-out over --ds-transition-duration-slow, supplied
by ui-theme's base sheet. Transitions pause during drags (data-dragging on
the frame, set for the whole gesture) and under prefers-reduced-motion.

.agents/notes/implemented/bug-fix/2026-07-22-collapsed-sidebar-control-rail.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
-2026-07-22-collapsed-sidebar-control-rail.md: 9f244010a1ec14eeafe707aedfffcf7e5bbe7736
-2026-07-22-collapsed-sidebar-control-rail.zh.md: 53007bf717404b151d0a2d1f673c20f111ee8234
+2026-07-22-collapsed-sidebar-control-rail.md: 90039110f4c1e97002fe45ebe42697452b2c6155
+2026-07-22-collapsed-sidebar-control-rail.zh.md: e5cd1c4911bbe02e10d2f1506943024bde862f12

.agents/notes/implemented/bug-fix/2026-07-22-collapsed-sidebar-control-rail.md

@@ -10,11 +10,11 @@ The sidebar close action persisted a zero width preference, and the layout mappe
 
 ## Decision
 
-The layout maps a closed sidebar (persisted width `0`) to the fixed `SIDEBAR_COLLAPSED` width of 60px: one 28px icon control between the sidebar's 16px horizontal paddings. The compact rail participates in the concession solver and retains its right border, while the stored expanded width remains untouched.
+The layout maps a closed sidebar (persisted width `0`) to the fixed `SIDEBAR_COLLAPSED` width of 56px: a 24px icon column between the sidebar's 16px horizontal paddings. The compact rail participates in the concession solver and retains its right border, while the stored expanded width remains untouched.
 
-`AppFrame` marks the sidebar collapsed from the persisted width preference rather than from the resolved track width, removes the resize handle while collapsed, and passes `collapsed` to the sidebar slot as owner props from the render site.
+`AppFrame` marks the sidebar collapsed from the persisted width preference rather than from the resolved track width, removes the resize handle while collapsed, and passes `collapsed` to the sidebar slot as owner props from the render site. Collapse and expand animate: the frame transitions `grid-template-columns` (and the remaining handle its `left`) on the deepsuite sider curve — `--ds-ease-in-out` over `--ds-transition-duration-slow`, both supplied by ui-theme's base sheet; transitions pause during drags and under `prefers-reduced-motion`.
 
-`SidebarRoot` reads the owner `collapsed` prop. Its collapsed render removes the brand, creation controls, search, and session tree from the rendered and accessibility trees — the body component unmounts, dropping its sessions subscription; the top control changes to `Expand sidebar`, and the bottom `Settings` control remains in the rail.
+`SidebarRoot` reads the owner `collapsed` prop. Its collapsed render is the rail: expand toggle, new session, search, and new workspace icons (each aligned with its expanded counterpart's behavior — the search icon expands the sidebar and focuses the search box) plus the `Settings` foot. The brand, capsule button, search field, and session tree leave the rendered and accessibility trees — the body component unmounts, dropping its sessions subscription.
 
 ## Alternatives considered
 
@@ -24,6 +24,6 @@ The layout maps a closed sidebar (persisted width `0`) to the fixed `SIDEBAR_COL
 
 ## Consequences
 
-- A collapsed sidebar reserves 60px instead of yielding the entire width to the center column. Expanding restores the persisted width and drag behavior.
+- A collapsed sidebar reserves 56px instead of yielding the entire width to the center column. Expanding restores the persisted width and drag behavior.
 - The settings entry remains visible but retains its existing placeholder behavior; this change does not introduce an account or settings screen.
 - Layout solver tests pin the compact width, sidebar component tests pin the visible controls, and the keyless real-bundle web smoke test pins collapse and recovery through the assembled client.

.agents/notes/implemented/bug-fix/2026-07-22-collapsed-sidebar-control-rail.zh.md

@@ -10,11 +10,11 @@ Status: implemented
 
 ## 决策
 
-布局将关闭的侧边栏（持久化宽度为 `0`）映射为固定的 `SIDEBAR_COLLAPSED` 宽度 60px：在侧边栏两侧各 16px 的水平内边距之间放置一个 28px 的图标控件。紧凑控制栏参与空间收缩求解，并保留右侧边框；已存储的展开宽度保持不变。
+布局将关闭的侧边栏（持久化宽度为 `0`）映射为固定的 `SIDEBAR_COLLAPSED` 宽度 56px：在侧边栏两侧各 16px 的水平内边距之间放置一列 24px 的图标控件。紧凑控制栏参与空间收缩求解，并保留右侧边框；已存储的展开宽度保持不变。
 
-`AppFrame` 根据持久化的宽度偏好标记侧边栏是否折叠，而不是根据求解后的轨道宽度来判断；折叠时移除尺寸调整手柄，并在渲染点把 `collapsed` 作为 owner props 传给侧边栏插槽。
+`AppFrame` 根据持久化的宽度偏好标记侧边栏是否折叠，而不是根据求解后的轨道宽度来判断；折叠时移除尺寸调整手柄，并在渲染点把 `collapsed` 作为 owner props 传给侧边栏插槽。折叠与展开带动画：frame 对 `grid-template-columns`（以及余下手柄的 `left`）应用 deepsuite 侧栏曲线过渡——`--ds-ease-in-out` 配 `--ds-transition-duration-slow`，两个变量由 ui-theme 的 base 表提供；拖拽期间和 `prefers-reduced-motion` 下过渡暂停。
 
-`SidebarRoot` 读取 owner 的 `collapsed` 属性。折叠状态下的渲染会将品牌标识、创建控件、搜索框和会话树从渲染树与可访问性树中移除——主体组件卸载，随之退订会话列表；顶部控件变为 `Expand sidebar`，底部的 `Settings` 控件则留在控制栏中。
+`SidebarRoot` 读取 owner 的 `collapsed` 属性。折叠渲染即控制栏：展开开关、新建会话、搜索、新建工作区四个图标（行为与展开态对应控件对齐——搜索图标会展开侧边栏并聚焦搜索框），加上底部的 `Settings`。品牌标识、胶囊按钮、搜索框和会话树离开渲染树与可访问性树——主体组件卸载，随之退订会话列表。
 
 ## 曾考虑的替代方案
 
@@ -24,6 +24,6 @@ Status: implemented
 
 ## 后果
 
-- 折叠的侧边栏占用 60px，而不是把全部宽度让给中心列。展开时恢复持久化宽度与拖动行为。
+- 折叠的侧边栏占用 56px，而不是把全部宽度让给中心列。展开时恢复持久化宽度与拖动行为。
 - 设置入口持续可见，但保留既有占位行为；本次改动不提供账户或设置页面。
 - 布局求解器测试固定紧凑宽度，侧边栏组件测试固定可见控件，基于真实构建产物的无密钥 Web 冒烟测试则通过组装后的客户端固定折叠与恢复行为。