refactor(grep): replace glob dependency with fs.readdirSync

- Add findFileRecursive function using native Node.js fs API
- Remove glob package from dependencies
- Add unit tests for findFileRecursive

🤖 GENERATED WITH ASSISTANCE OF [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode)

package.json

@@ -51,7 +51,6 @@
     "@code-yeongyu/comment-checker": "^0.5.0",
     "@openauthjs/openauth": "^0.4.3",
     "@opencode-ai/plugin": "^1.0.150",
-    "glob": "^13.0.0",
     "hono": "^4.10.4",
     "picomatch": "^4.0.2",
     "xdg-basedir": "^5.1.0",