docs(agent): add show-me review guidance

[BenSheridanEdwards]

Summary

• Install HumanLayer's show-me skill with its MIT license, pinned provenance, and lock metadata.
• Add NativeProof guidance for the smallest source-verified reviewer view only when it removes ambiguity.
• Keep tests, screenshots, reports, warnings, and uncertainty authoritative.
• Prevent automatic opening, publishing, or committing of HTML artifacts.

Proof

• npm run check
• npm test, 224 tests passed
• Generated project/device proof, or N/A: Not applicable. No generated project or device behaviour changed.

Reviewer view

• Policy chain: CLAUDE.md and AGENTS.md activate .claude/skills/show-me/NATIVEPROOF.md.
• .agents/DEFINITION_OF_DONE.md and this PR template carry the reviewer contract.

Risk

• Low. Repository guidance and agent tooling only.

Notes

• Full device coverage not run: no device or runtime behaviour changed.

PR Proof Law

• I followed .agents/DEFINITION_OF_DONE.md and .agents/skills/pr-inline-screenshot-proof/SKILL.md.
• Screenshots are not applicable because no rendered surface changed.
• The PR body has no bare screenshot links, local paths, relative paths, or proof placeholders.