Function qsa_score_rows 

pub fn qsa_score_rows(
    gpu: &dyn GpuBackend,
    kernel: KernelHandle,
    q: DevicePtr,
    block_keys: DevicePtr,
    scores: DevicePtr,
    rows: u32,
    n_blocks_max: u32,
    first_pos: u32,
    score_stride: u32,
    ratio: u32,
    n_heads: u32,
    hd: u32,
    stream: u64,
) -> Result<()>

Stage 2: per-row block scores, -inf beyond each row’s complete count.