feat: 搭建单元测试基础设施 — Bun test runner + 示例测试

添加 bunfig.toml 配置、test script，以及三组示例测试：
- src/utils/array.ts (intersperse, count, uniq)
- src/utils/set.ts (difference, intersects, every, union)
- packages/color-diff-napi (ansi256FromRgb, colorToEscape, detectLanguage 等)

41 tests, 0 failures.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

package.json

@@ -16,7 +16,8 @@
         "lint": "biome check src/",
         "lint:fix": "biome check --fix src/",
         "format": "biome format --write src/",
-        "prepare": "git config core.hooksPath .githooks"
+        "prepare": "git config core.hooksPath .githooks",
+        "test": "bun test"
     },
     "dependencies": {
         "@alcalzone/ansi-tokenize": "^0.3.0",