feat(FN-4999): recover completion handoff limbo safely

- Add completion handoff limbo recovery state to task storage and audit events for bounded self-healing retries
- Requeue eligible in-review tasks stuck after "Task marked done by agent" with grace-period, active-task, and merge-blocker safeguards
- Isolate executor run mutation context per task to prevent cross-task runId attribution leaks in scope-leak and completion logs
- Add reliability and executor regression tests covering limbo recovery, run-context isolation, and updated persistence behavior

Fusion-Task-Id: FN-4999

plugins/fusion-plugin-roadmap/src/store/__tests__/roadmap-store.test.ts

@@ -743,8 +743,8 @@ describe("RoadmapStore", () => {
   });
 
   describe("schema version", () => {
-    it("schema version is 84 after init", () => {
-      expect(db.getSchemaVersion()).toBe(84);
+    it("schema version is 85 after init", () => {
+      expect(db.getSchemaVersion()).toBe(85);
     });
   });