auto-open project from cwd and show Claude as primary

On desktop boot, main.dart calls project.open(cwd) to resolve the
git root. If a project opens successfully, the workspace activates
claude.primary instead of welcome. The _WorkspaceSlot now listens
to ProjectManager: when isOpen, Claude is always the visible
primary surface; when no project, welcome shows. This closes the
gap where the app loaded the project root but still displayed the
welcome screen as if no choice had been made.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/lib/main.dart

@@ -82,6 +82,13 @@ Future<void> main() async {
 
   await services.extensions.activateAll();
 
+  if (!kIsWeb) {
+    final opened = await services.project.open(Directory.current.path);
+    if (opened) {
+      services.panels.activateTab(Slots.workspace, 'claude.primary');
+    }
+  }
+
   runApp(ClideApp(services: services));
 }