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/components/NewPaneMenu.tsx

@@ -0,0 +1,44 @@
+import { Bot, MessageSquare, Plus, Terminal } from 'lucide-react';
+import {
+  DropdownMenu,
+  DropdownMenuContent,
+  DropdownMenuItem,
+  DropdownMenuTrigger,
+} from '@/components/ui/dropdown-menu';
+
+interface Props {
+  onAddPane: (kind: 'chat' | 'terminal' | 'agent') => void;
+  disabled?: boolean;
+}
+
+// v1.8 row-2 right cluster: mirrors the desktop Workspace.tsx Split dropdown.
+// Terminal and Agent items pass through to addSplitPane which already shows
+// "coming soon" toasts; rendering them here matches the Batch 3 workspace
+// model so the UI is forward-compatible with BooTerm/BooCoder.
+export function NewPaneMenu({ onAddPane, disabled }: Props) {
+  return (
+    <DropdownMenu>
+      <DropdownMenuTrigger asChild>
+        <button
+          type="button"
+          disabled={disabled}
+          className="inline-flex items-center justify-center min-h-[44px] min-w-[44px] rounded-full bg-muted/40 hover:bg-muted/70 text-foreground disabled:opacity-40 disabled:cursor-not-allowed shrink-0"
+          aria-label="New pane"
+        >
+          <Plus size={16} />
+        </button>
+      </DropdownMenuTrigger>
+      <DropdownMenuContent align="end">
+        <DropdownMenuItem onSelect={() => onAddPane('chat')}>
+          <MessageSquare size={14} /> New chat
+        </DropdownMenuItem>
+        <DropdownMenuItem onSelect={() => onAddPane('terminal')}>
+          <Terminal size={14} /> New terminal
+        </DropdownMenuItem>
+        <DropdownMenuItem onSelect={() => onAddPane('agent')}>
+          <Bot size={14} /> New agent
+        </DropdownMenuItem>
+      </DropdownMenuContent>
+    </DropdownMenu>
+  );
+}