Publish a GitHub Action to the Marketplace

[tabkram]

Why

The AI release-notes category lives on the GitHub Marketplace — github/copilot-release-notes, AbsaOSS/generate-release-notes, combinatrix-ai/release-note-writer, and the various ai-release-notes-action entries all ship that way.

docs/ci-cd.md explains how to wire the CLI into Actions, but there is no Marketplace listing. Anyone searching "release notes action" never finds this project.

Scope

• action.yml at the repository root, composite or Node-based.
• Inputs: from, to, env, provider, format, language, config-path, api-key.
• Outputs: generated markdown, the paths written, and token usage, so downstream steps can post to a release or a PR comment.
• A tagged major ref (v1) that moves, per Marketplace convention.
• Example workflows in docs/ci-cd.md: on tag push, and on release publish.

Acceptance criteria

• action.yml validates and runs from a clean checkout
• API key is read from secrets and never echoed into logs
• Outputs are consumable by a following step
• Two working example workflows documented
• Published to the GitHub Marketplace with a v1 moving tag
• Self-hosting: this repository uses the action for its own releases

Files

New action.yml, docs/ci-cd.md, .github/workflows/

Depends on

Worth doing after the quality issues land — a Marketplace listing is a first impression, and it should be made with the better output.