Use standard ja build and release workflows

[DanielThomas]

Summary

• reduce the build workflow to setup plus ja test --all
• reduce the release workflow to test plus ja maven deploy-central
• remove application self-assembly, development-JDK linking, and duplicate testing

Only ja requires end-to-end self-hosting. Ordinary tools should rely on the released ja GitHub action for testing and complete publication assembly.

Validation

• ja test --all — 9/9 tests passed
• workflow YAML parsed successfully
• current 0.4.1 release on Central has all six platform JMOD classifiers
• git diff --check