PR review buttons (Grok, Claude, Codex)

The buttons are plain Markdown links appended to the end of a PR description. Clicking one opens that AI's website with a prompt already typed in. Nothing runs in CI and no API key is needed. The whole feature is one Node script, one GitHub Actions workflow, and a marker string.

Reference implementation: tdk-cli-core — scripts/ai-review-buttons.mjs, .github/workflows/ai-review-buttons.yml, docs/contributing/04-review-a-pr.md.

What the reader sees

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# Review this PR in
[Grok badge](https://grok.com/?q=...) [Claude badge](https://claude.ai/new?q=...) [Codex badge](https://chatgpt.com/?q=...)

The prompt in every link is the same single sentence: