chore: consolidate test files into __tests__/ dirs and clean stray engine artifacts

- Move all co-located *.test.* files into sibling __tests__/ directories so the
  layout is consistent across packages (159 renames + content-rewrite moves).
  Updates relative imports, vi.mock specifiers, and __dirname/import.meta.url
  path resolutions where tests read fixtures from disk.
- Drop tracked tsc-emit alongside engine .ts sources (auth-storage/logger/
  skill-resolver/context-limit-detector/pi.{js,d.ts,*.map}). These were
  accidentally committed in a merge and the stale pi.js was masking a real
  test-mock vs source mismatch (tests imported "../pi.js" and vite preferred
  the stale build over pi.ts).
- Add packages/engine/.gitignore to block future src/*.{js,d.ts,map}.
- Refactor plugin pi-module seams (openclaw/paperclip/hermes) to ESM-import
  createFnAgent / promptWithFallback / describeModel from @fusion/engine
  instead of require()-ing packages/engine/src/pi.js. Adds @fusion/engine to
  the two plugin package.jsons that were missing it; exports describeModel
  from the engine public API.
- Fix engine test mocks now that they run against current pi.ts: add
  ModelRegistry.create static to mocks in pi.test.ts and pi-create-fn-agent
  .test.ts; switch three boundary-result toEqual assertions to toMatchObject
  so the new content/isError fields don't trip exact-match comparison.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/engine/src/__tests__/logger.test.ts

@@ -0,0 +1,88 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
+import {
+  createLogger,
+  schedulerLog,
+  executorLog,
+  triageLog,
+  mergerLog,
+  worktreePoolLog,
+  reviewerLog,
+  remoteNodeLog,
+} from "../logger.js";
+
+describe("createLogger", () => {
+  let logSpy: ReturnType<typeof vi.spyOn>;
+  let warnSpy: ReturnType<typeof vi.spyOn>;
+  let errorSpy: ReturnType<typeof vi.spyOn>;
+
+  beforeEach(() => {
+    logSpy = vi.spyOn(console, "log").mockImplementation(() => {});
+    warnSpy = vi.spyOn(console, "warn").mockImplementation(() => {});
+    errorSpy = vi.spyOn(console, "error").mockImplementation(() => {});
+  });
+
+  afterEach(() => {
+    logSpy.mockRestore();
+    warnSpy.mockRestore();
+    errorSpy.mockRestore();
+  });
+
+  it("formats log output as [prefix] message on stderr", () => {
+    const logger = createLogger("test");
+    logger.log("hello world");
+    expect(logSpy).not.toHaveBeenCalled();
+    expect(errorSpy).toHaveBeenCalledWith("\u0000fnlvl=info\u0000[test] hello world");
+  });
+
+  it("formats warn output as [prefix] message", () => {
+    const logger = createLogger("test");
+    logger.warn("something happened");
+    expect(warnSpy).toHaveBeenCalledWith("\u0000fnlvl=warn\u0000[test] something happened");
+  });
+
+  it("formats error output as [prefix] message", () => {
+    const logger = createLogger("test");
+    logger.error("failure");
+    expect(errorSpy).toHaveBeenCalledWith("\u0000fnlvl=error\u0000[test] failure");
+  });
+
+  it("passes extra arguments through", () => {
+    const logger = createLogger("test");
+    const err = new Error("boom");
+    logger.error("failed:", err);
+    expect(errorSpy).toHaveBeenCalledWith("\u0000fnlvl=error\u0000[test] failed:", err);
+  });
+
+  it("keeps log output off stdout", () => {
+    const logger = createLogger("x");
+    logger.log("a");
+    logger.warn("b");
+    logger.error("c");
+    expect(logSpy).not.toHaveBeenCalled();
+    expect(warnSpy).toHaveBeenCalledTimes(1);
+    expect(errorSpy).toHaveBeenCalledTimes(2);
+  });
+
+  it("pre-built instances use correct prefixes", () => {
+    schedulerLog.log("tick");
+    expect(errorSpy).toHaveBeenCalledWith("\u0000fnlvl=info\u0000[scheduler] tick");
+
+    executorLog.log("run");
+    expect(errorSpy).toHaveBeenCalledWith("\u0000fnlvl=info\u0000[executor] run");
+
+    triageLog.log("spec");
+    expect(errorSpy).toHaveBeenCalledWith("\u0000fnlvl=info\u0000[triage] spec");
+
+    mergerLog.log("merge");
+    expect(errorSpy).toHaveBeenCalledWith("\u0000fnlvl=info\u0000[merger] merge");
+
+    worktreePoolLog.log("prune");
+    expect(errorSpy).toHaveBeenCalledWith("\u0000fnlvl=info\u0000[worktree-pool] prune");
+
+    reviewerLog.log("review");
+    expect(errorSpy).toHaveBeenCalledWith("\u0000fnlvl=info\u0000[reviewer] review");
+
+    remoteNodeLog.log("stream");
+    expect(errorSpy).toHaveBeenCalledWith("\u0000fnlvl=info\u0000[remote-node] stream");
+  });
+});