- fix scalar prefill head_dim=32 out-of-bounds via G=4 dispatch - fix MMA decode 4D mask head indexing and invalid-row mask access - add q_head/kv_head divisibility and head-dim contiguity checks - validate split-KV scratch and decode out_buf layout in bindings - set max dynamic shared memory for scalar decode D=256 - cover scalar prefill D=32 in pure C test