Add automatic release generation workflow

[SnowCheetos]

Context

The project already has commit and PR generation machinery. It would be useful to add a similar release-oriented command/workflow that can produce release notes and optionally drive release creation.

Goals

• Add an auto-release feature that can summarize changes since the previous tag or release.
• Reuse the existing analysis, commit, and PR machinery where it makes sense.
• Support a dry-run mode that prints the proposed release notes without mutating GitHub state.
• Consider GitHub Releases integration once the generated output is reliable.

Acceptance criteria

• A user can generate release notes from local git history or a target range.
• The feature has tests for version/tag range selection and generated output shape.
• The workflow avoids surprising network or GitHub mutations unless explicitly requested.