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

.gitea/workflows/test.yaml

@@ -13,7 +13,8 @@ jobs:
     - uses: actions/setup-node@820762786026740c76f36085b0efc47a31fe5020 # v7.0.0
       with:
         node-version: '24'
-    - run: npm install
+    - uses: pnpm/action-setup@v4
+    - run: pnpm install --frozen-lockfile
       shell: bash
-    - run: npm test
+    - run: pnpm test
       shell: bash