feat(codegen): generate minecraft datapack output

[ofabiodev]

Summary

Adds deterministic Minecraft datapack generation from Puff IR.

Changes

• Generate pack metadata, functions, load/tick tags, commands, and runtime storage.
• Validate Minecraft versions, namespaces, resource paths, pack formats, and unsupported mappings.
• Add transactional output writing, golden tests, determinism coverage, and diagnostic tests.

Testing

cd src
go test ./...
go vet ./...

Notes

Supports Minecraft Java 1.21 through 1.21.6. Console output remains unsupported until its runtime mapping is defined.