feat(KB-088): clear failed status when moving tasks and improve error display

- Fix moveTask to clear status/error/worktree/blockedBy when moving from in-progress to todo/triage
- Add error message display in TaskCard for failed tasks with truncation
- Add prominent error alert in TaskDetailModal for failed tasks
- Refactor usage tracking: move from app/components to dashboard/src/
- Add usage.ts and usage.test.ts for centralized usage tracking
- Remove UsageIndicator and useUsageData from app/ directory
- Update styles.css for error display components
- Update executor tests for error handling
- Add changeset for patch release

packages/core/src/types.ts

@@ -148,11 +148,11 @@ export interface Task {
   validatorModelId?: string;
   /** Number of merge retry attempts made for this task (auto-merge conflict recovery) */
   mergeRetries?: number;
+  /** Error message from the last failure, if the task failed during execution */
+  error?: string;
   /** ISO-8601 timestamp of when the task last entered its current column.
    *  Used to sort cards within a column so that recently-moved cards appear at the top. */
   columnMovedAt?: string;
-  /** Error message from the last failure, if the task failed during execution */
-  error?: string;
   createdAt: string;
   updatedAt: string;
 }