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/dashboard/src/__tests__/claude-cli-probe.test.ts

@@ -0,0 +1,43 @@
+import { describe, expect, it } from "vitest";
+import { probeClaudeCli } from "../claude-cli-probe.js";
+
+/**
+ * These tests exercise the real probe — we deliberately do NOT mock
+ * `spawn`. The probe's job is to tell the truth about the local system,
+ * and mocking defeats that. Instead we:
+ *
+ *   1. Assert the shape is sound regardless of binary availability
+ *   2. Assert timeouts fire when the binary hangs (we don't have a
+ *      hanging binary fixture, so we cover the structural case only)
+ *   3. Let the suite pass whether or not `claude` is installed on the
+ *      test runner — both outcomes are legitimate.
+ *
+ * If you need mocked probe behavior for a higher-level route test, spy
+ * on `probeClaudeCli` at the import boundary rather than shimming spawn.
+ */
+describe("probeClaudeCli", () => {
+  it("returns a well-formed result whether or not claude is installed", async () => {
+    const result = await probeClaudeCli();
+    expect(typeof result.available).toBe("boolean");
+    expect(typeof result.probeDurationMs).toBe("number");
+    if (result.available) {
+      // When available: version string should come back populated.
+      expect(typeof result.version).toBe("string");
+    } else {
+      // When unavailable: reason must be populated so the UI can render.
+      expect(typeof result.reason).toBe("string");
+    }
+  });
+
+  it("respects a short timeout", async () => {
+    // Not a true hang test (we don't have a hanging binary), but
+    // confirms the timeoutMs option wires through and probe completes
+    // in a bounded window when using a very small timeout.
+    const result = await probeClaudeCli({ timeoutMs: 50 });
+    expect(result.probeDurationMs).toBeLessThan(5000);
+    // Either it completed fast enough or hit the timeout — both fine.
+    if (!result.available && result.reason?.includes("timed out")) {
+      expect(result.reason).toContain("50ms");
+    }
+  });
+});