Update dockerfile

[mincong-h]

The default Dockerfile does not work for pnpm workspace. This PR fixes it

• https://github.com/vertesia/studio/issues/1060

Testing

docker buildx build --platform linux/amd64 -t "vertesia/github-agent:latest" -f apps/github-agent/Dockerfile .

➜  github-agent git:(dockerfile|u=) vertesia agent run
! Corepack is about to download https://registry.npmjs.org/pnpm/-/pnpm-9.15.0.tgz

> @vertesia/github-agent@1.10.0 start /workspace/apps/github-agent
> node lib/main.js

Configuring logger on stdout
Create Runtime Logger for Temporal: INFO
(node:32) [DEP0040] DeprecationWarning: The `punycode` module is deprecated. Please use a userland alternative instead.
(Use `node --trace-deprecation ...` to show where the warning was created)
[09:50:38.034] INFO (llm-studio/32): Starting worker version: 1.0.0
[09:50:38.123] INFO (llm-studio/32): Getting temporal client cert pair from vault
    temporal: {
      "tlsCertificatePath": "tmprl_dev_zeno-worker_crt",
      "tlsPrivateKeyPath": "tmprl_dev_zeno-worker_key"
    }
[09:50:38.123] INFO (llm-studio/32): Getting secret from Google Secret Manager: tmprl_dev_zeno-worker_crt
[09:50:38.124] INFO (llm-studio/32): Getting secret from Google Secret Manager: tmprl_dev_zeno-worker_key

[mincong-h]

We need this because the build script is not available at the top level of the workspace

[mincong-h]

Make the comment compatible with the workspace