feat(FN-4948): complete Step 2 — wire identity guard into worktree provisioning

Fusion-Task-Id: FN-4948
Fusion-Task-Lineage: dc622643-4c3e-4217-9219-a6a6e5424427

packages/engine/src/__tests__/step-session-executor.test.ts

@@ -15,6 +15,10 @@ vi.mock("../worktree-hooks.js", () => ({
   installTaskWorktreeIdentityGuard: vi.fn().mockResolvedValue(undefined),
 }));
 
+vi.mock("../worktree-hooks.js", () => ({
+  installTaskWorktreeIdentityGuard: vi.fn().mockResolvedValue(undefined),
+}));
+
 // ── Shared test fixtures ──────────────────────────────────────────────
 
 function makePrompt(steps: string[]): string {