fix(agent-jobs): add heartbeat cancel and stale recovery

packages/backend/tests/unit/update-status.test.ts

@@ -107,3 +107,35 @@ describe('updateStatus terminal guard', () => {
     expect(job?.status).toBe('checks_running');
   });
 });
+
+describe('heartbeatWorkspace cancellation propagation', () => {
+  test('reports cancellation while refreshing the workspace heartbeat', async () => {
+    const t = convexTest(schema, modules);
+    const jobId = await seedJob(t, 'cancelled');
+
+    const result = await t.mutation(api.agentJobs.heartbeatWorkspace, {
+      workerToken: 'test-worker-token',
+      workerId: 'worker-1',
+      jobId,
+    });
+
+    expect(result).toEqual({ success: true, cancelRequested: true });
+    const job = await t.run(async (ctx) => await ctx.db.get(jobId));
+    expect(job?.status).toBe('cancelled');
+    expect(job?.workspaceStatus).toBe('active');
+    expect(job?.lastHeartbeatAt).toBeTypeOf('number');
+  });
+
+  test('reports no cancellation for an active job', async () => {
+    const t = convexTest(schema, modules);
+    const jobId = await seedJob(t, 'running');
+
+    const result = await t.mutation(api.agentJobs.heartbeatWorkspace, {
+      workerToken: 'test-worker-token',
+      workerId: 'worker-1',
+      jobId,
+    });
+
+    expect(result).toEqual({ success: true, cancelRequested: false });
+  });
+});