feat: add farewell helper to exercise CI and release pipeline

[ivanasabi]

Exercises all governed workflows end-to-end on this test consumer.

• Adds farewell() + TestFarewell in code/
• Adds a CHANGELOG [Unreleased] > Added entry

Trunk-based: merging this PR will auto-cut v0.1.0.

[github-actions]

Go Release Preview

• Current version (latest tag): none (first release)
• Proposed release tag: v0.1.0
• Next development version: CHANGELOG ## [Unreleased] re-seeded on the release commit (tag-only, no in-tree version)
• Release type: minor
• Expected merge strategy: Squash and merge

Changes

Added

• farewell helper alongside greeting, to exercise the CI and release pipeline end-to-end.

Changed

Fixed