Adopt Docs Agent completion contract

[chubes4]

Summary

• pin the accepted Docs Agent completion-contract revision and WP Codebox workflow producer
• require an evidence-backed update for PR Improve Figma Studio handoff diagnostics #100 Figma handoff diagnostics drift
• add positive bootstrap criteria and a bounded skills-maintenance source delta
• validate the consumer and producer contracts in CI

How to test

1. Run pnpm install --frozen-lockfile.
2. Check out Docs Agent a39d9db230eb9e0b72ed84465f4d61bd8dda1bab and WP Codebox 12a5bb19a97b89d0a78b502fc71adede5b122359.
3. Run DOCS_AGENT_DIR=/path/to/docs-agent WP_CODEBOX_DIR=/path/to/wp-codebox pnpm test.
4. Run pnpm build.
5. Run pnpm verify.
6. Run actionlint .github/workflows/*.yml.

Compatibility

This changes only documentation and skills maintenance workflows plus their validation contract. It does not change generated plugin runtime behavior or extension interfaces.

Relates to Automattic/docs-agent#166
Source drift: #100

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode with GPT-5.6-sol
• Used for: Updated workflow contracts, tests, and contributor documentation with Chris reviewing and owning the change.