feat(HAI-065): add file-scope overlap detection with blockedBy tracking

- Add blockedBy field to Task type and core store
- Update scheduler to set blockedBy when deferring tasks due to file-scope overlap
- Render file-scope overlap badge on TaskCard in dashboard
- Add tests for blockedBy store logic, scheduler deferral, and TaskCard badge
- Simplify and refactor existing executor, triage, and CLI command code

packages/engine/src/restart.integration.test.ts

@@ -464,7 +464,7 @@ describe("Scheduler after restart", () => {
     scheduler.stop();
 
     expect(store.moveTask).toHaveBeenCalledWith("HAI-070", "in-progress");
-    expect(store.updateTask).toHaveBeenCalledWith("HAI-070", { status: null });
+    expect(store.updateTask).toHaveBeenCalledWith("HAI-070", { status: null, blockedBy: null });
     expect(onSchedule).toHaveBeenCalledWith(todoTask);
   });