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/core/src/store.ts

@@ -267,6 +267,7 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
       if (toColumn === "done") {
         task.status = undefined;
         task.worktree = undefined;
+        task.blockedBy = undefined;
       }
 
       await this.atomicWriteTaskJson(dir, task);
@@ -281,7 +282,7 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
 
   async updateTask(
     id: string,
-    updates: { title?: string; description?: string; prompt?: string; worktree?: string; status?: string | null },
+    updates: { title?: string; description?: string; prompt?: string; worktree?: string; status?: string | null; blockedBy?: string | null },
   ): Promise<Task> {
     return this.withTaskLock(id, async () => {
       const dir = this.taskDir(id);
@@ -295,6 +296,11 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
       } else if (updates.status !== undefined) {
         task.status = updates.status;
       }
+      if (updates.blockedBy === null) {
+        task.blockedBy = undefined;
+      } else if (updates.blockedBy !== undefined) {
+        task.blockedBy = updates.blockedBy;
+      }
       task.updatedAt = new Date().toISOString();
 
       await this.atomicWriteTaskJson(dir, task);
@@ -564,6 +570,7 @@ export class TaskStore extends EventEmitter<TaskStoreEvents> {
     task.column = "done";
     task.worktree = undefined;
     task.status = undefined;
+    task.blockedBy = undefined;
     task.updatedAt = new Date().toISOString();
 
     await this.atomicWriteTaskJson(dir, task);