feat(FN-1690): add RoadmapStore with SQLite persistence

- Implement RoadmapStore with CRUD operations for roadmaps, milestones, and features
- Add roadmap schema migration v32 with roadmaps, roadmap_milestones, and roadmap_features tables
- Add covering indexes for deterministic ordering within roadmaps and milestones
- Wire RoadmapStore access via TaskStore.getRoadmapStore()
- Update architecture.md documentation with RoadmapStore persistence
- Add comprehensive tests for RoadmapStore CRUD and ordering
- Update db.test.ts with schema v32 assertions
- Add UpdateInput type imports to task-documents.test.ts
- Export RoadmapStore from core index.ts

packages/core/src/run-audit.test.ts

@@ -465,7 +465,7 @@ describe("Run Audit", () => {
     });
 
     it("schema version is bumped to 28", () => {
-      expect(db.getSchemaVersion()).toBe(31);
+      expect(db.getSchemaVersion()).toBe(32);
     });
   });
 });