chore(cleanup): remove retired Python/Nix pr_agent server entirely
- delete src/*.py (run_server, start_server, callback_server, health-check,
auto_merge_bot, trivial_merge, sync-key) — Python pr_agent retired
- delete scripts/{setup_app,setup_all,generate_manifest,generate_manifest_domain}.py
- delete flake.nix + flake.lock + flakehub-publish-rolling.yaml — Nix build retired
- deploy.yml: Nix/Python CI → Bun CI (setup-bun, typecheck, tests,
bun build --compile → scp binary → swap /opt/.../pr-agent-bun →
restart pr-agent-bun.service → health check :4023)
- README: document Bun era; legacy Python/Nix section
- pr-agent-bun.service is the sole production server (port 4023)
asepharyana
570b5b8707