feat: migrate plugin config to runtime consumer

[lusu007]

Pull Request

Description

Migrates plugin-config Paper and Velocity modules to the new runtime-consumer conventions. The modules now declare loader dependencies on plugin-grounds-runtime, no longer declare gRPC/protobuf as plugin implementation dependencies, and keep protobuf on the test runtime classpath only.

Type of Change

• 🐛 Bug fix
• ✨ New feature
• 💥 Breaking change
• ♻️ Refactoring
• 📚 Documentation
• 🔧 Chore

Related Issues

• Fixes #

Testing

• Unit tests pass
• Manual testing completed
• New tests added for new functionality
• ./gradlew test
• ./gradlew spotlessApply
• ./gradlew build
• jar tf paper/build/libs/plugin-config-paper.jar | rg "^(io/grpc|com/google/protobuf|kotlinx/coroutines|kotlin/)" returned no matches
• jar tf velocity/build/libs/plugin-config-velocity.jar | rg "^(io/grpc|com/google/protobuf|kotlinx/coroutines|kotlin/)" returned no matches

Checklist

• I have performed a self-review of my own code
• Tests have been added/updated and pass (if needed)
• Documentation has been updated (if needed)