Potassium

**Current state: **

Potassium is now an independent Fabric rendering-engine prototype with its own startup path, OpenGL capability negotiation, resident GPU world-data pipeline, page-based world-data growth beyond the single-buffer 2 GiB mapping limit, chunk upload and unload handling, and incremental block-change synchronization. It is still a backend milestone rather than a finished player-facing renderer: vanilla terrain rendering is not replaced yet, and GPU meshing, indirect draw submission, final culling, and release-grade performance claims are still in progress.