fix: consolidate DagTask types, fix REST fallback shape, fix lint noqa

- Extract shared DagTask/DagTaskStatus types into www/app/lib/dagTypes.ts
- Re-export from useWebSockets.ts and UserEventsProvider.tsx
- Fix browse page REST fallback: dag_status is list[dict] directly, not {tasks: [...]}
- Add missing # noqa: PLC0415 for fork-safe deferred imports

www/app/lib/UserEventsProvider.tsx

@@ -7,25 +7,8 @@ import { useAuth } from "./AuthProvider";
 import { z } from "zod";
 import { invalidateTranscriptLists, TRANSCRIPT_SEARCH_URL } from "./apiHooks";
 
-export type DagTaskStatus =
-  | "queued"
-  | "running"
-  | "completed"
-  | "failed"
-  | "cancelled";
-
-export type DagTask = {
-  name: string;
-  status: DagTaskStatus;
-  started_at: string | null;
-  finished_at: string | null;
-  duration_seconds: number | null;
-  parents: string[];
-  error: string | null;
-  children_total: number | null;
-  children_completed: number | null;
-  progress_pct: number | null;
-};
+import type { DagTask } from "./dagTypes";
+export type { DagTask, DagTaskStatus } from "./dagTypes";
 
 const DagStatusContext = React.createContext<Map<string, DagTask[]>>(new Map());