Function ssm_replay_row_bytes 

pub fn ssm_replay_row_bytes(qkvz_elems: usize, nv: usize) -> usize

One cached verify-row of GDN inputs for replay, per SSM layer: the deinterleaved qkvz row (qkvz_elems BF16 — what conv1d consumes; Z included, the gated norm needs it) + the gate/beta row (nv * 2 FP32). These are exactly the per-token tensors the WY verify kernels read (ConvGdnArgs::deinterleaved / gates_buf rows), and re-running them through the sequential conv+GDN path from the checkpoint reproduces the snapshot the dropped intermediates used to hold.