Card: standardized form with hero

Standardize card: usage-first

fp4-train: add fp4_mm, the native Blackwell NVFP4 tensor-core matmul (10x over the dequant path)

Uploaded using `kernel-builder`.

Correct fp4-train card: SR/EF beat round-to-nearest in NVFP4 weight-storage training

Add fp4-train source, tests, and model card

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initial commit