feat: Support multi-package PyPI publishing #1175

Problem

The current PyPI publishing support assumes one Python package per repo — it always builds at the worktree root. Repos like myk-org/pi-config have 2 Python packages in different directories:

• Root: myk-pi-tools (hatchling, pyproject.toml)
• packages/pi-sidecar/: pi-sidecar-client (setuptools, packages/pi-sidecar/pyproject.toml)

Currently there's no way to specify subdirectories or build/publish multiple packages.

Current Behavior

• Config schema: pypi: {token: "..."} — flat, no package paths
• push_handler.py → upload_to_pypi(): on tag push, checks out tag into worktree, runs uv build --sdist at worktree root, then twine upload — only finds the root package
• runner_handler.py → run_install_python_module(): PR check runs uvx pip wheel at worktree root — one package only
• check_run_handler.py: registers one status check (PYTHON_MODULE_INSTALL_STR)
• github_api.py: self.pypi: dict[str, str] — flat dict with just token

Proposed Solution

1. Schema change (webhook_server/config/schema.yaml)

Add optional packages list to pypi:

pypi:
  token: <PYPI TOKEN>
  packages:           # optional — defaults to ["."] (repo root)
    - "."
    - "packages/pi-sidecar"

Backward compatible — if packages is absent, behaves like today (root only).

2. Config loading (webhook_server/libs/github_api.py)

Add pypi_packages property that resolves to ["."] when packages key is absent.

3. Push handler (webhook_server/libs/handlers/push_handler.py)

Loop upload_to_pypi() over each package directory:

• Build each package in its own subdirectory
• Upload each package separately
• Create issue on failure per package

4. Runner handler (webhook_server/libs/handlers/runner_handler.py)

Loop run_install_python_module() over each package dir. Option to register separate check runs per package (e.g., Python module install [myk-pi-tools]) or keep one combined check.

5. Check run handler (webhook_server/libs/handlers/check_run_handler.py)

If separate checks per package: register PYTHON_MODULE_INSTALL_STR per package name. If combined: no change needed.

Files to change

Backward Compatibility

Zero breaking changes — pypi: {token: "..."} without packages defaults to root-only, exactly as today.

Done

• Schema updated with packages array under pypi
• github_api.py parses pypi.packages with ["."] default
• push_handler.py loops upload_to_pypi over each package dir
• runner_handler.py loops run_install_python_module over each package dir
• examples/config.yaml updated with multi-package example
• Tests cover multi-package config, build, and upload