[stackyard-release]

Summary

• Date Unreleased as 1.20.0 and add its compare link.
• Bump api/package.json to 1.20.0.

Testing
The changelog gate ran in release mode before this branch was pushed. Merging this tags the release and publishes the image.

Checklist

• Stays within the project constraints: one container, no runtime dependencies, no build step (see CONTRIBUTING.md).
• Tests added or updated for new logic, and the full suite, lint, and typechecks pass.
• Docs updated if behavior or configuration changed.