Add docs release-readiness verification

[rogerchappel]

Summary

• add a local docs release-readiness checker for required docs, markdown emptiness, README release links, and stale docs workflow placeholder text
• replace the docs workflow placeholder with a real pnpm-backed docs check
• include docs verification in the local release:check path

Verification

• pnpm run docs:check
• pnpm run docs:check && pnpm run check
• pnpm run release:check

Notes

The queue entries for many nearby repos were already fixed on origin/main, so this PR targets the remaining stackforge docs workflow placeholder.