chore: migrate package manager from npm to pnpm (#110)

This PR migrates the package manager from `npm` to `pnpm`.

### Changes:
- Replaced `package-lock.json` with `pnpm-lock.yaml` and `pnpm-workspace.yaml`.
- Updated `.gitea/workflows/test.yaml` to include `pnpm/action-setup@v4` and use `pnpm install` / `pnpm test`.
- Updated `renovate.json` to match `pnpm` manager and execute `pnpm install --frozen-lockfile` and `pnpm run build`.
- Updated `.pre-commit-config.yaml` to exclude `pnpm-lock.yaml` from `pretty-format-yaml`.
- Updated documentation in `README.md` and `GEMINI.md`.
- Rebuilt `dist/index.js`.Reviewed-on: #110

renovate.json

@@ -8,12 +8,12 @@
   "packageRules": [
     {
       "matchManagers": [
-        "npm"
+        "pnpm"
       ],
       "postUpgradeTasks": {
         "commands": [
-          "npm ci",
-          "npm run build"
+          "pnpm install --frozen-lockfile",
+          "pnpm run build"
         ],
         "fileFilters": [
           "dist/index.js"