feat(FN-3857): auto-recover merge deadlocks by recovering already merged ca

Adds auto-recovery for merge deadlocks when candidates have already been merged on main (FN-3857), including tests, documentation updates in AGENTS.md, and a patch changeset for the `@runfusion/fusion` package.

Fusion-Task-Id: FN-3857

.changeset/fn-3857-auto-recover-merge-deadlocks.md

@@ -0,0 +1,5 @@
+---
+"@runfusion/fusion": patch
+---
+
+Add automatic recovery for board-level merge deadlocks by promoting retry-exhausted already-landed review tasks to done, clearing stale `blockedBy` references on todo tasks when blockers are terminal or deadlocked, and excluding paused in-review worktrees from scheduler overlap `activeScopes` so paused blockers cannot repeatedly re-stamp downstream tasks.

AGENTS.md

@@ -178,6 +178,10 @@ Port 4040 is the production dashboard port. A user's live dashboard session is t
 - Run `kill`, `kill -9`, `pkill`, or `killall` against processes on port 4040
 - Start a test server on port 4040 — always use `--port 0` for random free port
 
+## Architecture
+
+- Merge deadlock self-healing now has three layered defenses: `SelfHealingManager.recoverAlreadyMergedReviewTasks()` and `SelfHealingManager.clearStaleBlockedBy()` in `packages/engine/src/self-healing.ts`, plus the paused-aware in-review scope filter in `packages/engine/src/scheduler.ts` (`inReviewWithWorktree` excludes `paused` tasks). Together these auto-finalize already-landed retry-exhausted review tasks, clear stale downstream blockers, and prevent paused review cards from re-blocking overlap dispatch.
+
 ## Engine Process Rules
 
 The engine (`packages/engine`) runs the executor, merger, scheduler, IPC host, and dashboard-facing activity loop on a single Node event loop. **Blocking that loop stalls every task concurrently in-flight.**

packages/engine/src/__tests__/self-healing.test.ts

@@ -2600,7 +2600,7 @@ describe("SelfHealingManager", () => {
       managerWithRecovery.stop();
     });
 
-    it("filters out non-candidates", async () => {
+    it("filters out non-candidates but still evaluates paused failed candidates", async () => {
       const managerWithRecovery = new SelfHealingManager(store, {
         rootDir: "/tmp/test-project",
         getExecutingTaskIds: () => new Set(["FN-executing"]),
@@ -2613,12 +2613,17 @@ describe("SelfHealingManager", () => {
         { id: "FN-executing", column: "in-review", paused: false, status: "failed", mergeRetries: 3, mergeDetails: undefined, log: [] },
         { id: "FN-confirmed", column: "in-review", paused: false, status: "failed", mergeRetries: 3, mergeDetails: { mergeConfirmed: true }, log: [] },
       ]);
+      mockedExecSync.mockImplementation(() => "" as any);
 
       const result = await managerWithRecovery.recoverAlreadyMergedReviewTasks();
 
       expect(result).toBe(0);
       expect(store.updateTask).not.toHaveBeenCalled();
       expect(store.moveTask).not.toHaveBeenCalled();
+      expect(mockedExecSync).toHaveBeenCalledWith(
+        expect.stringContaining("Fusion-Task-Id: FN-paused"),
+        expect.any(Object),
+      );
 
       managerWithRecovery.stop();
     });

packages/engine/src/self-healing.ts

@@ -1807,7 +1807,6 @@ export class SelfHealingManager {
    *
    * Candidate filter:
    * - `column === "in-review"`
-   * - not paused
    * - `status === "failed"`
    * - `(mergeRetries ?? 0) >= MAX_AUTO_MERGE_RETRIES`
    * - `mergeDetails.mergeConfirmed !== true`
@@ -1830,7 +1829,6 @@ export class SelfHealingManager {
       const tasks = await this.store.listTasks({ column: "in-review", slim: true });
       const candidates = tasks.filter((task) =>
         task.column === "in-review" &&
-        !task.paused &&
         task.status === "failed" &&
         (task.mergeRetries ?? 0) >= MAX_AUTO_MERGE_RETRIES &&
         task.mergeDetails?.mergeConfirmed !== true &&