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/core/src/types.ts

@@ -115,7 +115,7 @@ export const COLUMN_DESCRIPTIONS: Record<Column, string> = {
 export const VALID_TRANSITIONS: Record<Column, Column[]> = {
   triage: ["todo"],
   todo: ["in-progress", "triage"],
-  "in-progress": ["in-review"],
+  "in-progress": ["in-review", "todo"],
   "in-review": ["done", "in-progress"],
   done: [],
 };