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/useProjectGit.ts

@@ -0,0 +1,41 @@
+import { useEffect, useState } from 'react';
+import { api } from '@/api/client';
+import type { GitMeta } from '@/api/types';
+
+const POLL_INTERVAL_MS = 30_000;
+
+// Live-ish git meta for the project header indicator. Backed by the server's
+// 30s cache, so a 30s client poll plus the cache TTL bounds total staleness
+// to ~60s in the worst case. Returns null while the first fetch is in flight
+// or if the request failed.
+export function useProjectGit(projectId: string | null | undefined): GitMeta | null {
+  const [meta, setMeta] = useState<GitMeta | null>(null);
+
+  useEffect(() => {
+    if (!projectId) {
+      setMeta(null);
+      return;
+    }
+    let cancelled = false;
+
+    const fetchOnce = () => {
+      api.projects
+        .git(projectId)
+        .then((m) => {
+          if (!cancelled) setMeta(m);
+        })
+        .catch(() => {
+          if (!cancelled) setMeta(null);
+        });
+    };
+
+    fetchOnce();
+    const t = setInterval(fetchOnce, POLL_INTERVAL_MS);
+    return () => {
+      cancelled = true;
+      clearInterval(t);
+    };
+  }, [projectId]);
+
+  return meta;
+}