Publish to PyPI for a real `pip install pellet-pilot`

[ctopherwilliams]

Problem / motivation

pyproject.toml and the pellet console script already work via pip install -e . from a clone, but there's still a "clone + venv" barrier for anyone who just wants the tool without touching the source. A real PyPI release would let a new user run one command (or pipx install pellet-pilot) to get the pellet CLI.

Proposed solution

• Verify the package builds cleanly with python -m build (flat py-modules layout — double check presets/*.yaml actually gets bundled by [tool.setuptools.package-data] in a non-editable install, since editable installs resolve paths differently and this hasn't been verified for a real wheel).
• Add a release workflow (tag-triggered, or manual workflow_dispatch) that builds and publishes via twine/PyPI trusted publishing.
• Update the README quickstart once this works, with the pip install -e . path kept as the "hacking on it" alternative.

Alternatives considered

A single-file/pipx-only distribution without a PyPI listing — narrower reach than an actual PyPI package, and pipx install <git-url> is already possible today without this work, so PyPI is the meaningful next step.