feat(mobile): v1.8 tab switcher + branch indicator + git_status tool

Mobile header is now two rows. Row 1: hamburger | project · branch
indicator (live via GET /api/projects/:id/git, 30s poll) | ModelPicker |
FolderTree. Row 2: pane-switcher pill (hand-rolled BottomSheet) +
NewPaneMenu. Chat-within-pane navigation hidden on mobile; users switch
panes via the sheet. Cross-tab status sync via chat_status frames
published from inference.ts at working/idle/error transitions; StatusDot
component renders amber-pulse/green/red/gray on each pane row and on
desktop ChatTabBar tabs. Level 1 git awareness exposes a read-only
git_status tool to the model, backed by services/git_meta.ts (execFile
+ 2s timeout + 30s cache). Workspace.tsx now receives panes/chats hooks
as props (hoisted into Session.tsx) so the header pill shares state
with the pane grid.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/src/hooks/useSidebar.ts

@@ -171,6 +171,7 @@ function applyEvent(prev: SidebarResponse, event: import('./sessionEvents').Sess
     case 'chat_archived':
     case 'chat_unarchived':
     case 'chat_deleted':
+    case 'chat_status':
       return prev;
     case 'project_archived': {
       const next = prev.projects.filter((p) => p.id !== event.project_id);