PhysX PE 5.11.0-alpha.3 source build kit

Portable build-source kit for the published PhysX PE 5.11.0-alpha.3 runtime. Contains the genuine Git bundle, exact source inventory, clone instructions and complete licenses. Clone the included bundle to recreate source commit53c0cd99d0695a23b89047bde0f000fdecaaa363.

Original custom additions are MIT within their stated scope. NVIDIA PhysX/Blast/Flow, fabmax, webidl-util and other dependencies retain their notices and licenses. This is an attributed integration, not a clean-room SDK rewrite. No additional compiled-runtime, Engine or realtime claim follows from this source delivery. The seven-asset runtime release is separate.