feat(FN-5242): add merge queue storage and lease API to task store

- docs(FN-5242): complete Step 7 — document merge queue storage
- docs(FN-5242): complete Step 5 — add changeset and exports
- fix(FN-5242): order merge queue audit assertions chronologically
- test(FN-5242): complete Step 4 — cover merge queue leasing
- feat(FN-5242): complete Step 2 — add merge queue lease API
- feat(FN-5242): complete Step 1 — add mergeQueue schema v89

Fusion-Task-Id: FN-5242

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

@@ -743,8 +743,8 @@ describe("RoadmapStore", () => {
   });
 
   describe("schema version", () => {
-    it("schema version is 88 after init", () => {
-      expect(db.getSchemaVersion()).toBe(88);
+    it("schema version is 89 after init", () => {
+      expect(db.getSchemaVersion()).toBe(89);
     });
   });