Fix missing pos increment for last prefill and check that in gemma_test. Thanks to @ufownl for pointing this out. Change argument lists to QBatch with accessors. Increase default seq_len to 8k. PiperOrigin-RevId: 771937385
move row_ptrs into MatMulEnv Consistent arg order: layer, activations, kv_cache, env PiperOrigin-RevId: 767886386
weights, mat: zero-initialize padding, required since the MatMul "avoid B decompress" optimization. PiperOrigin-RevId: 767562313