feat(FN-3364): sort done tasks by most recent completion

- Sort Done column and list views by most recent completion timestamp to keep recent work visible first
- Update dashboard and task management docs to document done-column recency ordering behavior
- Preserve merge-active task state across verification bounce paths and board/list rendering updates
- Forward removeDependencyReferences in deleteTask flows and treat finish_reason=repeat as a soft-stop in engine executor

Fusion-Task-Id: FN-3364

docs/dashboard-guide.md

@@ -16,6 +16,7 @@ Features:
 - Inline quick entry creation
 - PR/issue badges with live updates
 - GitHub provenance marker on task cards imported from GitHub (`sourceType: github_import`), shown alongside existing footer metadata like timers
+- Column ordering semantics: `triage`, `todo`, `in-progress`, `in-review`, and `archived` stay priority-ordered; `done` is ordered by most recent completion first (`columnMovedAt`, then `updatedAt`, then `createdAt` fallback)
 
 ![Board view](./screenshots/dashboard-overview.png)
 

docs/task-management.md

@@ -86,6 +86,10 @@ Fusion task columns:
 5. **done** — merged/finalized
 6. **archived** — preserved history, optionally cleaned from filesystem
 
+Board ordering behavior:
+- Active work columns (`triage`, `todo`, `in-progress`, `in-review`) remain priority-ordered.
+- The `done` column is recency-ordered by completion time (newest first), using `columnMovedAt` as primary and falling back to `updatedAt` then `createdAt` for legacy tasks.
+
 ### Lifecycle commands
 
 ```bash