feat(FN-3280): harden reviewState persistence, API, and PR feedback sync

Merges reviewState hardening (FN-3280 steps 2-3: hardened persistence, API fixes, and PR feedback sync), stepIndex reconciliation for task updates (FN-3757), roadmap route context extraction into the fusion-plugin-roadmap plugin (FN-3160), and shared state snapshots for mesh sync with autostash hard

Fusion-Task-Id: FN-3280

packages/engine/src/__tests__/pr-comment-handler.test.ts

@@ -213,6 +213,12 @@ describe("PrCommentHandler", () => {
               expect.objectContaining({ source: "github-pr", status: "queued" }),
             ]),
           }),
+          reviewState: expect.objectContaining({
+            source: "pull-request",
+            items: expect.arrayContaining([
+              expect.objectContaining({ source: "github-pr", body: "Please add tests" }),
+            ]),
+          }),
         }),
       );
       expect(mockStore.moveTask).toHaveBeenCalledWith("FN-001", "in-progress");