feat: add working-directory input to change script execution directory

- Add working-directory input to action.yml
- Implement process.chdir() in main.ts before script execution
- Users can now specify working directory without modifying scripts

Closes #426

dist/index.js

@@ -65092,6 +65092,11 @@ async function main() {
     }
     const github = getOctokit(token, opts, retry, requestLog);
     const script = core.getInput('script', { required: true });
+    const workingDirectory = core.getInput('working-directory');
+    if (workingDirectory) {
+        core.info(`Changing working directory to ${workingDirectory}`);
+        process.chdir(workingDirectory);
+    }
     // Wrap getOctokit so secondary clients inherit retry, logging,
     // orchestration ID, and the action's retries input.
     // Deep-copy opts to prevent shared references with the primary client.