Function chunk_states 

pub(crate) fn chunk_states<B: Backend>(
    xhat_blchp: F<B, 5>,
    bhat_blchr: F<B, 5>,
    d_bhl: &F<B, 3>,
    l_bhll: &F<B, 4>,
    h_in_bhpr: &F<B, 4>,
) -> F<B, 5>

One chunk of cache-frame states h̃[t] = dₜ·h₋ + Σ_{j≤t,c} L[t,j]·x̂[j,c] ⊗ b̂[j,c] — the channel axis is folded into the write index for one batched GEMM.

Shapes

• xhat_blchp / bhat_blchr: one chunk of the combined injections.
• returns states_bhlpr.