b11866

metal : remove mul_mm_id amax rescaling (#30924)

The src1 power-of-two rescale in kernel_mul_mm_id is superseded by the
per expert-token amax scaling done in the compute graph
(ref: #30861), which keeps the
MoE down-projection activations within f16 range before the op runs.

Drop the two-stage reduction kernels, their scratch buffer and the
GGML_PREC_F32 dispatch added in #26223,
as well as the test cases that drive MUL_MAT_ID src1 out of f16 range.

Assisted-by: pi:llama.cpp/ggml-org/Qwen3.8-Flash-Next-GGUF (MacBook, M5 Max, 128GB)

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• https://github.com/ggml-org/llama.cpp/attestations/59468925

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