Module generations 

Generational collection with card table write barriers.

• Young generation: Small region set (~4-8MB), bump-allocated, collected frequently.
• Old generation: Larger region set, collected less frequently.
• Promotion: Objects surviving N young collections are copied to old gen.
• Card table: 512-byte cards tracking old→young pointers (write barrier at store sites).

Structs

CardTable

Card table for tracking old→young pointers.

GenerationalCollector

Generational collector state.