fix(ci): 修復 CI 失敗問題

- lewooogo-core: 新增 placeholder 測試檔 (vitest)
- api: 修復 I001 import 排序 (ruff --fix)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

packages/lewooogo-core/src/__tests__/index.test.ts

@@ -0,0 +1,19 @@
+/**
+ * lewooogo-core 基礎測試
+ * Phase 16 CI 修復 (2026-03-26)
+ */
+
+import { describe, it, expect } from 'vitest'
+
+describe('lewooogo-core', () => {
+  it('should export core interfaces', async () => {
+    // 動態 import 避免 build 前測試失敗
+    const core = await import('../index')
+    expect(core).toBeDefined()
+  })
+
+  it('should have PluginRegistry', async () => {
+    const core = await import('../index')
+    expect(core.PluginRegistry).toBeDefined()
+  })
+})