feat(HAI-055): add failed task status handling with retry support

- Set task status to 'failed' on execution failure in engine executor
- Add failed indicator styling on TaskCard component
- Add POST /tasks/:id/retry API endpoint and client function
- Add retry button in TaskDetailModal for failed tasks
- Add tests for failed indicator, retry endpoint, and modal behavior

packages/dashboard/src/routes.test.ts

@@ -16,6 +16,7 @@ function createMockStore(overrides: Partial<TaskStore> = {}): TaskStore {
     mergeTask: vi.fn(),
     getSettings: vi.fn().mockResolvedValue({}),
     updateSettings: vi.fn(),
+    logEntry: vi.fn().mockResolvedValue(undefined),
     ...overrides,
   } as unknown as TaskStore;
 }
@@ -143,6 +144,61 @@ describe("GET /tasks/:id", () => {
   });
 });
 
+describe("POST /tasks/:id/retry", () => {
+  let store: TaskStore;
+
+  beforeEach(() => {
+    store = createMockStore();
+  });
+
+  function buildApp() {
+    const app = express();
+    app.use(express.json());
+    app.use("/api", createApiRoutes(store));
+    return app;
+  }
+
+  it("retries a failed task and moves it to todo", async () => {
+    const failedTask = { ...FAKE_TASK_DETAIL, status: "failed" };
+    const movedTask = { ...FAKE_TASK_DETAIL, column: "todo", status: undefined };
+    (store.getTask as ReturnType<typeof vi.fn>).mockResolvedValue(failedTask);
+    (store.updateTask as ReturnType<typeof vi.fn>).mockResolvedValue(failedTask);
+    (store.moveTask as ReturnType<typeof vi.fn>).mockResolvedValue(movedTask);
+
+    const res = await REQUEST(buildApp(), "POST", "/api/tasks/HAI-001/retry", JSON.stringify({}), {
+      "Content-Type": "application/json",
+    });
+
+    expect(res.status).toBe(200);
+    expect(store.updateTask).toHaveBeenCalledWith("HAI-001", { status: undefined });
+    expect(store.moveTask).toHaveBeenCalledWith("HAI-001", "todo");
+  });
+
+  it("returns 400 when task is not in failed state", async () => {
+    const activeTask = { ...FAKE_TASK_DETAIL, status: "executing" };
+    (store.getTask as ReturnType<typeof vi.fn>).mockResolvedValue(activeTask);
+
+    const res = await REQUEST(buildApp(), "POST", "/api/tasks/HAI-001/retry", JSON.stringify({}), {
+      "Content-Type": "application/json",
+    });
+
+    expect(res.status).toBe(400);
+    expect(res.body.error).toContain("not in a failed state");
+  });
+
+  it("returns 400 when task is not in in-progress column", async () => {
+    const doneTask = { ...FAKE_TASK_DETAIL, column: "done", status: "failed" };
+    (store.getTask as ReturnType<typeof vi.fn>).mockResolvedValue(doneTask);
+
+    const res = await REQUEST(buildApp(), "POST", "/api/tasks/HAI-001/retry", JSON.stringify({}), {
+      "Content-Type": "application/json",
+    });
+
+    expect(res.status).toBe(400);
+    expect(res.body.error).toContain("not in a failed state");
+  });
+});
+
 describe("Attachment routes", () => {
   const FAKE_ATTACHMENT: TaskAttachment = {
     filename: "1234-screenshot.png",

packages/dashboard/src/routes.ts

@@ -108,6 +108,23 @@ export function createApiRoutes(store: TaskStore, options?: ServerOptions): Rout
     }
   });
 
+  // Retry failed task
+  router.post("/tasks/:id/retry", async (req, res) => {
+    try {
+      const task = await store.getTask(req.params.id);
+      if (task.column !== "in-progress" || task.status !== "failed") {
+        res.status(400).json({ error: "Task is not in a failed state" });
+        return;
+      }
+      await store.updateTask(req.params.id, { status: undefined });
+      await store.logEntry(req.params.id, "Retry requested from dashboard");
+      const updated = await store.moveTask(req.params.id, "todo");
+      res.json(updated);
+    } catch (err: any) {
+      res.status(500).json({ error: err.message });
+    }
+  });
+
   // Upload attachment
   router.post("/tasks/:id/attachments", upload.single("file"), async (req, res) => {
     try {