feat(sidebar): 文件页与文件变动页 UIUX 重构 + 全局组件抽取

文件页（FileTree/TreePanel）
- Ctrl/Cmd 多选 + Shift 按可见行序连选（Esc/点空白/右键收敛），批量条支持复制路径、批量删除（共享 ConfirmDialog + 顺序 fsRemove）
- Git 变更着色：行名按状态上色 + M/A/D/U 徽标，目录按 dirHasChanges 着色，非仓库静默降级（数据来自共享 git 状态存储）
- 新建文件夹：fs.mkdir 路由 + mkdirWorkspaceEntry + 内联输入行（Enter/Esc/blur/IME 守卫）
- 性能：FileRow/DirRow memo（含反向验证）、搜索 hidden 停车不再卸载树、level 拉取世代守卫 + AbortController、fs.tree truncated 提示、use-dir-watch 入参 memo
- 拖拽上传视觉 token 化（硬编码色清零）；可见性下传后隐藏页签停止轮询
- 右键「打开方式」改为复用 DSH 自带 open-in-app（宿主探测的关联应用 + 文件管理器显示）

文件变动页（changes/diff）
- 36px 头（宿主 SegmentedControl）+ 单一 ChangeRow + SectionHeader 分组 + 吸底提交条单状态行 + 历史独立空态
- 修掉：双份空态、暂存失败 unhandled rejection、手动刷新被丢、仓库切换刷新两次、worktree 清单缺 repoRoot、工作树被自动切走、预览持旧快照、恢复高度未 clamp、session ops 无谓轮询
- DiffPane/DiffTab 共用 use-git-diff；修掉 DiffPane 的 untracked 预览从不渲染

全局组件与宿主接入
- 新增 src/client/ui（IconButton/Chip/SectionHeader/Notice/ConfirmDialog/StatusBadge + 共享 git 状态存储）
- 新增 src/client/open-in-app.ts（宿主 open-in-app 客户端适配），删除自研 open-with 全链路与 open.external 路由
- 客户端 inject 补 remote / remote.session：缺声明时 ctx.get('remote').session 会抛出并把整个面板打成错误条（真实挂载 lane 抓到）
- 词典：+25 键 / -20 openWith* / -noChanges，20 份同步

验证：typecheck / lint / test（126 文件 1322 通过）/ build 全绿；
DSH_CMD='npx -y --package @deepseek-ai/dsh@0.1.7-rc.1 dsh' pnpm test:mount 7/7 通过（含 tab sweep 与 perf lane）

src/client/layout.css

@@ -78,64 +78,3 @@ body[data-dsh-sidebar-dragging] #root [data-dsh-center-col] {
   #root [data-dsh-center-col] {
     transition: none;
   }
-}
-
-/* Context-menu submenu flip (viewport clamping for the portaled menus).
- *
- * The ui-primitives Menu clamps its main portal list into the viewport but
- * positions nested submenus with static CSS only — anchored at the parent
- * row's bottom, growing UP and to the RIGHT — with no clamp whatsoever.
- * Both defaults are the worst case for our menus: a tall "open with" submenu
- * escapes past the viewport top when the row menu opens near the top, and
- * past the right edge in a narrow workbench pane (a pane can be far narrower
- * than the card 218 + gap + submenu 165 a submenu needs).
- *
- * menu-flip.ts publishes `data-dsh-sidebar-submenu` on <body> — with the
- * words "down" and/or "left" — for exactly the lifetime of one of OUR
- * submenu-bearing menus (FileTree row menu, TabBar tab menu). The tokens
- * flip the growth direction; the attribute's absence restores the
- * primitive's own geometry untouched, and host-owned menus are never
- * affected because they never open while the attribute exists (each side
- * closes on the other's outside pointerdown).
- *
- * No max-height/overflow scroll cap here on purpose: overflow clipping
- * would cut the submenu's ::before hover bridge (the corridor that keeps
- * itemWrap's mouseleave from closing the card mid-crossing). */
-
-/* Visual tether, part 1 — the parent row stays lit while its submenu is
- * open. The primitive only styles :hover, so once the pointer crossed into
- * the side card the parent row's fill cleared and the floating card read as
- * unrelated. The Menu marks the open parent row with aria-expanded="true"
- * (host-rendered, stable), so the same hover token re-applies for the
- * submenu's whole lifetime. */
-body[data-dsh-sidebar-submenu] div[role="menu"] button[aria-expanded="true"] {
-  background: var(--dsw-alias-interactive-bg-hover);
-}
-
-/* Visual tether, part 2 — the side card hugs its parent (10px → 4px gap),
- * with the ::before hover corridor narrowed to match. Ordered BEFORE the
- * flip overrides below so their left/right flips still win. */
-body[data-dsh-sidebar-submenu] div[role="menu"] div[role="menu"] {
-  left: calc(100% + 4px);
-}
-
-body[data-dsh-sidebar-submenu] div[role="menu"] div[role="menu"]::before {
-  left: -4px;
-  width: 4px;
-}
-
-body[data-dsh-sidebar-submenu~="down"] div[role="menu"] div[role="menu"] {
-  top: -4px;
-  bottom: auto;
-}
-
-body[data-dsh-sidebar-submenu~="left"] div[role="menu"] div[role="menu"] {
-  left: auto;
-  right: calc(100% + 4px);
-}
-
-/* The hover bridge follows the card to the left side of the parent row. */
-body[data-dsh-sidebar-submenu~="left"] div[role="menu"] div[role="menu"]::before {
-  left: auto;
-  right: -4px;
-}