Use Child_Process to pull code?

Yes, that is a simple opinion.

Do it with one simple file:

const spawnSync = require('node:child_process').spawnSync;
const http = require('node:http');

const pullScript = `cd project1-folder && git pull && php artisan optimize && cd ../project2-folder && git pull && php artisan optimize && cd ../project3-folder && git pull && npm i && npm run build && supervisorctl restart project3:`;

const hostname = '127.0.0.1';
const port = 3000;
const server = http.createServer(async (req, res) => {
    const result = spawnSync('su', ["-l","user1",'bash', '-c', pullScript], { encoding: 'utf-8' });

  res.statusCode = 200;
  res.setHeader('Content-Type', 'text/plain');

  const allLines = result.output
    ? result.output
        .filter(Boolean) // remove null or undefined
        .map((output) => res.write(output.toString()))
        .join('\n')
    : '';

  console.log(allLines)
  res.end('Done\n');
});
server.listen(port, hostname, () => {
  console.log(`Server running at http://${hostname}:${port}/`);
});

Now, you can write an API to call http://localhost:3000 to pull 3 project. You can `composer update` or something more.