feat: inline rotation matrices in Metal shader + C round-trip test PrismML-Eng#21

- Inlined turbo-matrices.h directly into ggml-metal.metal (256KB)
  to fix JIT compilation failure with #include
- Added C round-trip test (test-turbo-quant.c):
  turbo3 cosine=0.906, turbo4 cosine=0.966 — matches Python prototype
- Metal library loads successfully ("loaded in 5.9 sec")
- Model runs on Metal but output quality needs debugging
  (Metal quantize/dequantize may have a bug vs the working C version)

C round-trip PROVES the algorithm works in C. Metal shader needs
debugging — likely an issue with the dequantize chunk addressing
or the large constant arrays in thread-local memory.

Co-Authored-By: [email protected]
Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Author: TheTom