chore: 测试框架从 bun:test 迁移到 vitest

- 36 个 test 文件 bun:test → vitest
- Bun.spawn() → execFileSync('tsx', ...)
- Bun.file() → readFileSync
- import.meta.dir → import.meta.dirname (tests) / __dirname (CLI source)
- 删除 bun-types devDep
- 添加 vitest + tsx devDep
- CLI shebang bun → node
- 30/36 test files pass, 558/617 tests pass

Refs #62

tsconfig.json

@@ -1,6 +1,6 @@
 {
   "compilerOptions": {
-    "types": ["bun-types"],
+    "types": ["node"],
     "target": "ES2022",
     "module": "ESNext",
     "moduleResolution": "bundler",