Make Ruby block guide examples match documented JSON

[nicklambourne]

Summary

• Replace all 21 minimal Ruby block-guide snippets with public-API constructions that emit the exact JSON shown beside each example.
• Make the Ruby docs check compare full payloads, require a Ruby and JSON example for every block section, and continue executing the higher-level component and other guide snippets.

Verification

• All 28 Ruby guide snippets execute, and every block payload matches its documented JSON.
• Full Docusaurus build passes, including generated references, search/language/version checks, Ruby API rendering, and historical docs contracts.
• Docs TypeScript typecheck and git diff --check pass.

Stacked on #374. Draft; do not merge until the Ruby train is ready.