fix engine build and test resolution

packages/engine/src/pi-create-kb-agent.test.ts

@@ -1,4 +1,5 @@
 import { beforeEach, describe, expect, it, vi } from "vitest";
+import type { PathLike } from "node:fs";
 
 const createAgentSessionMock = vi.fn();
 const createCodingToolsMock = vi.fn(() => []);
@@ -18,7 +19,7 @@ const settingsManagerInMemoryMock = vi.fn(() => ({ kind: "settings-manager" }));
 const setFallbackResolverMock = vi.fn();
 const reloadMock = vi.fn(async () => {});
 const execSyncMock = vi.fn(() => "");
-const existsSyncMock = vi.fn(() => false);
+const existsSyncMock = vi.fn((_path: PathLike) => false);
 const readFileSyncMock = vi.fn(() => "{}");
 
 vi.mock("node:child_process", () => ({

packages/engine/vitest.config.ts

@@ -1,10 +1,16 @@
 import { defineConfig } from "vitest/config";
 import { availableParallelism } from "node:os";
+import { resolve } from "node:path";
 
 const defaultMaxWorkers = Math.max(1, Math.min(4, Math.ceil(availableParallelism() / 8)));
 const maxWorkers = Number.parseInt(process.env.VITEST_MAX_WORKERS ?? String(defaultMaxWorkers), 10);
 
 export default defineConfig({
+  resolve: {
+    alias: {
+      "@fusion/core": resolve(__dirname, "../core/src/index.ts"),
+    },
+  },
   test: {
     include: ["src/**/*.test.ts"],
     maxWorkers,