Exercise the automated beta release pipeline #111

Summary

Exercise the complete reviewed release path with a beta release and verify that
version bumping, pull requests, stable tagging, GitHub Release creation, and
downstream publishing work together.

Prerequisites

• The release implementation is merged.
• stable and branch protections are configured.
• RELEASE_GH_TOKEN is configured.
• Trusted Publishers are registered on PyPI.

Publishing decision

The current workflow publishes a GitHub Release to production PyPI, including a
prerelease. Confirm one option before dispatching:

• Beta releases may be published to production PyPI.
• Or first change the workflow so prereleases go to TestPyPI and only stable
  releases go to PyPI.

Do not run this rehearsal until that decision is recorded.

Steps

1. Dispatch Release on main.
2. Select mode=beta.
3. Review the generated synchronized version bump PR.
4. Confirm the expected result, currently 0.4.0b0 -> 0.4.0b1.
5. Merge the bump PR into main.
6. Confirm the workflow opens the main -> stable release PR.
7. Review and merge the release PR into stable.
8. Verify tag, GitHub Release, package publishing, and container workflows.

Version checks

• Commitizen computes the expected beta version.
• Every workspace package version is updated.
• Every cross-workspace dependency pin is updated.
• uv.lock records the same version for every workspace package.
• No old workspace version remains in a pyproject.toml.

Workflow checks

• The bump PR is created against main.
• The main -> stable release PR is created automatically.
• Re-running preparation does not create a duplicate bump.
• Merging to stable creates v<version>.
• The GitHub Release is marked as a prerelease.
• pypi-publish.yml is triggered.
• docker-build.yml is triggered.

Post-release checks

• All three packages are available at the beta version.
• The installed closure uses exact matching internal dependency versions.
• Basic imports and CLI smoke tests pass.
• Any follow-up issues are linked to the umbrella issue.

Acceptance criteria

• The beta release completes through reviewed pull requests only.
• Stable tagging and GitHub Release creation work.
• Downstream workflows trigger correctly.
• The synchronized package closure is published and installable.