fix(gui): keep sidebar controls when collapsed

.agents/notes/implemented/bug-fix/2026-07-22-collapsed-sidebar-control-rail.i18n.yaml

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+# Bilingual-pair consistency record (docs/i18n/README.md): the git blob hash of each
+# 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: 27e7d0e18a20b2ea6de8128f9c3518279ec21aca
+2026-07-22-collapsed-sidebar-control-rail.zh.md: bfbb5230f952e49960142bb5ce090dc6753487ec

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

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+# Agent Note: A collapsed sidebar retains its control rail
+
+Status: implemented
+
+English | [中文](2026-07-22-collapsed-sidebar-control-rail.zh.md)
+
+## Problem
+
+The sidebar close action persisted `open: false`, and the layout mapped that preference to a zero-width grid track. The only sidebar toggle and the settings entry both lived inside that clipped track, so closing the sidebar removed every visible recovery control. Reloading preserved the closed preference and reproduced the lockout.
+
+## Decision
+
+The layout maps a closed sidebar 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.
+
+`AppFrame` marks the sidebar collapsed from the persisted `open` preference rather than from a zero resolved width. It keeps the sidebar slot mounted but removes the resize handle while collapsed.
+
+`SidebarRoot` subscribes to the derived open boolean. Its collapsed render removes the brand, creation controls, search, and session tree from the rendered and accessibility trees; the top control changes to `Expand sidebar`, and the bottom `Settings` control remains in the rail.
+
+## Alternatives considered
+
+- **Render an expand button over the center column** — rejected because it recovers only the toggle, not the persistent settings area, and splits sidebar chrome across two package owners.
+- **Keep a zero-width grid track and let the rail overflow it** — rejected because the rail would overlap the center column and leave hit testing and responsive geometry disconnected from the grid.
+- **Keep the complete sidebar tree mounted and hide it with clipping** — rejected because hidden controls remain in the semantic tree and continue subscribing and rendering even though only two controls belong in the collapsed state.
+
+## Consequences
+
+- A collapsed sidebar reserves 60px 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

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+# Agent Note: 侧边栏折叠后保留控制栏
+
+Status: implemented
+
+[English](2026-07-22-collapsed-sidebar-control-rail.md) | 中文
+
+## 问题
+
+侧边栏关闭操作会持久化 `open: false`，布局再将该偏好映射为宽度为零的网格轨道。侧边栏唯一的开关与设置入口都位于这个被裁切的轨道内，因此关闭侧边栏会移除所有可见的恢复控件。页面重新加载时仍会读取关闭偏好，从而再次陷入无法恢复的状态。
+
+## 决策
+
+布局将关闭的侧边栏映射为固定的 `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。
+
+`AppFrame` 根据持久化的 `open` 偏好标记侧边栏是否折叠，而不是根据求解后的宽度是否为零来判断。它让侧边栏插槽保持挂载，但在折叠时移除尺寸调整手柄。
+
+`SidebarRoot` 订阅派生的布尔型打开状态。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；顶部控件变为 `Expand sidebar`，底部的 `Settings` 控件则留在控制栏中。
+
+## 曾考虑的替代方案
+
+- **在中心列上方渲染展开按钮**：不予采纳，因为这只能恢复开关，无法保留常驻设置区域，同时还会让侧边栏 UI 由两个包（package）分别持有。
+- **保留宽度为零的网格轨道，让控制栏溢出显示**：不予采纳，因为控制栏会与中心列重叠，还会使命中测试和响应式几何关系脱离网格布局。
+- **保持完整侧边栏树挂载，并通过裁切将其隐藏**：不予采纳，因为隐藏控件仍留在语义树中，而且会继续订阅和渲染，尽管折叠状态下只需要两个控件。
+
+## 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。
+- 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。