Harden YAML catalogs and static output

[gregjotau]

Summary

• intern identical generated static UTF-8 segments without adding request-time work
• reject misplaced catalogs and non-canonical YAML extensions
• track invalid YAML extension variants as incremental KSP inputs
• add focused compiler coverage and remove an existing Kotlin warning
• update GitHub Actions to their Node 24 major versions
• prepare patch release 0.5.1

Verification

• ./gradlew clean build --rerun-tasks --console=plain
• generated example template blob shrank from 1677 to 1637 bytes
• build completes without compiler warnings