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__/auth-storage.test.ts

@@ -0,0 +1,93 @@
+import { afterEach, beforeEach, describe, expect, it } from "vitest";
+import { mkdirSync, writeFileSync, existsSync } from "node:fs";
+import { mkdtemp } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { createFusionAuthStorage, getFusionAuthPath } from "../auth-storage.js";
+
+describe("createFusionAuthStorage", () => {
+  // HOME override required — createFusionAuthStorage() has no dir parameter
+  const originalHome = process.env.HOME;
+  let homeDir: string;
+
+  beforeEach(async () => {
+    homeDir = await mkdtemp(join(tmpdir(), "fusion-engine-auth-"));
+    process.env.HOME = homeDir;
+  });
+
+  afterEach(() => {
+    if (originalHome === undefined) {
+      delete process.env.HOME;
+    } else {
+      process.env.HOME = originalHome;
+    }
+  });
+
+  it("writes to Fusion auth and reads legacy Pi auth as fallback", async () => {
+    const legacyAgentDir = join(homeDir, ".pi", "agent");
+    mkdirSync(legacyAgentDir, { recursive: true });
+    writeFileSync(
+      join(legacyAgentDir, "auth.json"),
+      JSON.stringify({
+        openrouter: { type: "api_key", key: "legacy-openrouter-key" },
+        minimax: { type: "api_key", key: "legacy-minimax-key" },
+      }),
+    );
+
+    const authStorage = createFusionAuthStorage();
+    authStorage.set("openrouter", { type: "api_key", key: "fusion-openrouter-key" });
+
+    expect(await authStorage.getApiKey("openrouter")).toBe("fusion-openrouter-key");
+    expect(await authStorage.getApiKey("minimax")).toBe("legacy-minimax-key");
+    expect(authStorage.get("minimax")).toEqual({ type: "api_key", key: "legacy-minimax-key" });
+    expect(existsSync(getFusionAuthPath(homeDir))).toBe(true);
+  });
+
+  it("reads non-expired legacy Pi OAuth credentials as fallback", async () => {
+    const legacyAgentDir = join(homeDir, ".pi", "agent");
+    mkdirSync(legacyAgentDir, { recursive: true });
+    writeFileSync(
+      join(legacyAgentDir, "auth.json"),
+      JSON.stringify({
+        "openai-codex": {
+          type: "oauth",
+          access: "legacy-access-token",
+          refresh: "legacy-refresh-token",
+          expires: Date.now() + 60_000,
+        },
+      }),
+    );
+
+    const authStorage = createFusionAuthStorage();
+
+    expect(await authStorage.getApiKey("openai-codex")).toBe("legacy-access-token");
+  });
+
+  it("does not use expired legacy Pi OAuth credentials", async () => {
+    const legacyAgentDir = join(homeDir, ".pi", "agent");
+    mkdirSync(legacyAgentDir, { recursive: true });
+    writeFileSync(
+      join(legacyAgentDir, "auth.json"),
+      JSON.stringify({
+        "openai-codex": {
+          type: "oauth",
+          access: "expired-access-token",
+          refresh: "legacy-refresh-token",
+          expires: Date.now() - 60_000,
+        },
+      }),
+    );
+
+    const authStorage = createFusionAuthStorage();
+
+    expect(await authStorage.getApiKey("openai-codex")).toBeUndefined();
+  });
+
+  it("does not create missing legacy Pi auth files", async () => {
+    const authStorage = createFusionAuthStorage();
+
+    expect(await authStorage.getApiKey("openrouter")).toBeUndefined();
+    expect(existsSync(join(homeDir, ".pi", "agent", "auth.json"))).toBe(false);
+    expect(existsSync(join(homeDir, ".pi", "auth.json"))).toBe(false);
+  });
+});