Borrow packed inputs and codec tables; return owned bf16 K/V or null.
Only the measured eager D256/k8v3/B1/H4/fp16/group32 regime is eligible.
Other regimes continue through the existing joint decoder or original codec.
N affects dispatch size but is never a shader template parameter.
Borrow packed inputs and codec tables; return owned bf16 K/V or null. Only the measured eager D256/k8v3/B1/H4/fp16/group32 regime is eligible. Other regimes continue through the existing joint decoder or original codec. N affects dispatch size but is never a shader template parameter.