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

GEMINI.md

@@ -19,7 +19,7 @@ This project uses [Vitest](https://vitest.dev/) for testing. The tests are locat
 To run the tests locally, use the following command:
 
 ```bash
-npm test
+pnpm test
 ```
 
 ### Testing Pipeline
@@ -29,6 +29,6 @@ The tests are automatically run on every push and workflow dispatch using a Gite
 The Gitea workflow does the following:
 
 1.  Checks out the code.
-2.  Sets up Node.js.
-3.  Installs the dependencies using `npm install`.
-4.  Runs the tests using `npm test`.
+2.  Sets up Node.js and pnpm.
+3.  Installs the dependencies using `pnpm install`.
+4.  Runs the tests using `pnpm test`.