Add self-hosted GCP runner for CI/CD workflows

[baogorek]

Summary

• Migrates all GitHub Actions workflows from ubuntu-latest to self-hosted GCP runner
• Improves performance and resource availability for CI/CD jobs
• Uses n2-standard-16 spot instance (64GB RAM, 32GB swap) in policyengine-research GCP project

Changes

• Updated .github/workflows/pr.yaml - all 5 jobs now use runs-on: self-hosted
  • Lint
  • check-version
  • Quick-Feedback
  • YAML-NonStructural
  • Structural-and-Python
• Updated .github/workflows/push.yaml - all 6 jobs now use runs-on: self-hosted
  • Lint
  • versioning
  • YAML-NonStructural
  • Structural-and-Python
  • Publish
  • Deploy
• Added changelog entry documenting infrastructure change

Test plan

• [ ] Verify self-hosted runner is online and registered in GitHub Actions
• [ ] Push this PR and confirm workflows pick up jobs on self-hosted runner
• [ ] Monitor all CI jobs complete successfully on self-hosted environment
• [ ] Verify GCP service account authentication still works
• [ ] Confirm PyPI publish and deployment steps work correctly

Infrastructure notes

Runner VM is managed via:

• VM name: pe-us-runner
• Start/stop: gcloud compute instances start/stop pe-us-runner --zone=us-central1-a
• Cost: ~$180/month running, ~$8/month stopped
• Setup documented in ~/devl/code-snippets/gcp/github-runners/

🤖 Generated with Claude Code

[PavelMakarchuk]

Do the github check now run sequentially? I believe in the current version they all run simultaneously

[PavelMakarchuk]

Do the github check now run sequentially? I believe in the current version they all run simultaneously

If so, this is adding about an hour to the entire runtime of the tests

[PavelMakarchuk]

Do the github check now run sequentially? I believe in the current version they all run simultaneously

@baogorek lmk if you have thoughts on runtime, maybe I misread the logs when they were running