feat(FN-4625): complete Step 7 — verification and docs updates

Fusion-Task-Id: FN-4625
Fusion-Task-Lineage: c1d9b414-b5dd-4786-ba51-0b8adec4acf5

packages/engine/src/__tests__/worktree-acquisition-backend.test.ts

@@ -23,6 +23,7 @@ describe("acquireTaskWorktree backend wiring", () => {
   const task = { id: "FN-1", title: "Task", description: "Desc", branch: null, worktree: null } as any;
   const store = {
     updateTask: vi.fn().mockResolvedValue(undefined),
+    pauseTask: vi.fn().mockResolvedValue(undefined),
     logEntry: vi.fn().mockResolvedValue(undefined),
   } as any;
 
@@ -30,6 +31,7 @@ describe("acquireTaskWorktree backend wiring", () => {
     execMock.mockReset();
     store.updateTask.mockClear();
     store.logEntry.mockClear();
+    store.pauseTask.mockClear();
   });
 
   it("uses native backend by default and emits no worktrunk audit", async () => {

packages/engine/src/worktree-acquisition.ts

@@ -21,6 +21,7 @@ import {
 } from "./worktrunk-installer.js";
 import {
   handleWorktrunkOperationFailure,
+  type WorktreeOperationResult,
   type WorktrunkOpName,
 } from "./worktrunk-failure-handler.js";
 import type { RunAuditor } from "./run-audit.js";
@@ -125,7 +126,7 @@ export async function acquireTaskWorktree(opts: AcquireTaskWorktreeOptions): Pro
       runContext,
       runAudit: audit,
       notify: ({ op: failedOp, stderr: failedStderr }) => notifyFallback(failedOp, failedStderr),
-      nativeFallback: nativeFallback as (() => Promise<any>) | undefined,
+      nativeFallback: nativeFallback as (() => Promise<WorktreeOperationResult>) | undefined,
     });
     if (disposition.kind === "fallback-native") {
       return disposition.result;