feat(FN-4625): complete Step 4 — add self-healing worktrunk pause guardrail

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

packages/engine/src/__tests__/reliability-interactions/worktrunk-failure.test.ts

@@ -0,0 +1,60 @@
+import { describe, expect, it, vi } from "vitest";
+import { EventEmitter } from "node:events";
+import type { Task, TaskStore } from "@fusion/core";
+import { SelfHealingManager } from "../../self-healing.js";
+
+vi.mock("../../worktree-pool.js", async () => {
+  const actual = await vi.importActual<any>("../../worktree-pool.js");
+  return { ...actual, isUsableTaskWorktree: vi.fn().mockResolvedValue(true) };
+});
+
+function makeTask(overrides: Partial<Task> = {}): Task {
+  return {
+    id: "FN-4625",
+    title: "FN-4625",
+    description: "task",
+    column: "in-progress",
+    dependencies: [],
+    steps: [],
+    currentStep: 0,
+    branch: "fusion/fn-4625",
+    worktree: "/tmp/fn-4625",
+    createdAt: new Date().toISOString(),
+    updatedAt: new Date().toISOString(),
+    ...overrides,
+  } as Task;
+}
+
+function makeStore(tasks: Task[]): TaskStore & EventEmitter {
+  const emitter = new EventEmitter();
+  return Object.assign(emitter, {
+    getSettings: vi.fn(async () => ({ maintenanceIntervalMs: 0, globalPause: false, enginePaused: false })),
+    listTasks: vi.fn(async ({ column, includeArchived }: any = {}) => tasks.filter((task) => {
+      if (!includeArchived && task.column === "archived") return false;
+      return !column || task.column === column;
+    })),
+    updateTask: vi.fn(async () => undefined),
+    logEntry: vi.fn(async () => undefined),
+    getTask: vi.fn(async () => tasks[0]),
+  }) as unknown as TaskStore & EventEmitter;
+}
+
+describe("reliability interactions: worktrunk failure", () => {
+  it("self-healing skips reclaim for tasks paused by worktrunk failures", async () => {
+    const store = makeStore([
+      makeTask({ paused: true, pausedReason: "worktrunk_operation_failed" }),
+    ]);
+
+    const manager = new SelfHealingManager(store, {
+      rootDir: process.cwd(),
+      getExecutingTaskIds: () => new Set(),
+    });
+
+    const inspectSpy = vi.spyOn(manager as any, "inspectOrphanedBranch");
+    const recovered = await manager.reclaimStaleActiveBranches();
+
+    expect(recovered).toBe(0);
+    expect(inspectSpy).not.toHaveBeenCalled();
+    expect(store.updateTask).not.toHaveBeenCalled();
+  });
+});