Fix stuck loading state for deleted/invalid workspaces

When a workspace is deleted or doesn't exist:
- Previously: selectedWorkspace persisted in localStorage, causing eternal "Loading workspace..."
- Now: Validate workspace exists on mount and clear invalid selection

Added validation effect that:
- Checks if selected workspace ID exists in workspaceMetadata
- Clears selection if workspace was deleted
- Also clears URL hash to prevent re-selection on reload

Fixes edge cases:
- Workspace deleted while app was closed
- URL with invalid workspace ID (#workspace=invalid-id)
- Workspace removed from another instance

Author: ammar-agent

src/App.tsx

@@ -255,6 +255,23 @@ function AppInner() {
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }, []);
 
+  // Validate selected workspace exists (clear if workspace was deleted)
+  useEffect(() => {
+    if (selectedWorkspace && workspaceMetadata.size > 0) {
+      const exists = workspaceMetadata.has(selectedWorkspace.workspaceId);
+      if (!exists) {
+        console.warn(
+          `Workspace ${selectedWorkspace.workspaceId} no longer exists, clearing selection`
+        );
+        setSelectedWorkspace(null);
+        // Also clear URL hash if present
+        if (window.location.hash) {
+          window.history.replaceState(null, "", window.location.pathname);
+        }
+      }
+    }
+  }, [selectedWorkspace, workspaceMetadata, setSelectedWorkspace]);
+
   const openWorkspaceInTerminal = useCallback((workspacePath: string) => {
     void window.api.workspace.openTerminal(workspacePath);
   }, []);