EncoderCache.empty constructor
Fresh cache sized for a stack of numLayers blocks each with
numKvHeads KV-head slots (equal to the Q-head count for
standard MHA; smaller for GQA).
Implementation
factory EncoderCache.empty(int numLayers, int numKvHeads) => EncoderCache(
List<MHACache>.generate(
numLayers,
(_) => MHACache.empty(numKvHeads),
growable: false,
),
);