fix(chat): invalidate workspace pending tasks cache on manual stop

When user manually stops a chat, only the per-session pending task cache
was cleared. The sidebar reads the workspace-level aggregate pending
tasks query, which remained stale — causing the loading spinner to keep
spinning. Now invalidate the aggregate cache too.

Closes MUL-1384

packages/views/chat/components/chat-page.tsx

@@ -179,7 +179,10 @@ export function ChatPage() {
       qc.setQueryData(chatKeys.pendingTask(activeSessionId), {});
       qc.invalidateQueries({ queryKey: chatKeys.messages(activeSessionId) });
     }
-  }, [pendingTaskId, activeSessionId, qc]);
+    if (wsId) {
+      qc.invalidateQueries({ queryKey: chatKeys.pendingTasks(wsId) });
+    }
+  }, [pendingTaskId, activeSessionId, wsId, qc]);
 
   const handleSelectAgent = useCallback(
     (agent: Agent) => {