Function build_moe_row_adapter_decode 

pub fn build_moe_row_adapter_decode(
    adapter_slots: &[i32],
    padded_n: usize,
    active: i32,
    has_moe_lora: bool,
) -> Vec<i32>

SOLID Incr-4 (batched decode fold): build the per-row [padded_n] i32 adapter map the device-side MoE gather-BGMV fold reads. One token per sequence at decode, so a per-row map IS a per-seq map (no top_k expansion — the kernel indexes row_adapter[row / top_k]).

Per row i, resolve_moe_lora_route(adapter_slots[i], active, has_moe_lora):

• Fold (owns the installed active adapter) ⇒ write active (>= 0 when an adapter is resident — the kernel only tests the SIGN, and the single active adapter’s per-expert tables are folded). When no adapter is installed (has_moe_lora == false) active is -1, so the row correctly skips.
• Skip (base / non-active) ⇒ -1 (device kernel skips the row — MoE’s < 0 = base semantics, NOT the attention seq_slot -1 → active).
• Refuse (non-active adapter present) ⇒ -1 DEFENSIVELY. A Refuse batch is bailed host-side before this map is ever uploaded (stamp_decode_moe_batch + the decode_batch_compute_main pre-lookup guard); mapping to base here means a leaked Refuse row folds NOTHING rather than mis-folding the wrong adapter.
• pad rows (i >= adapter_slots.len()) ⇒ -1 (skip).

Pure + GPU-free so the routing is unit-testable without hardware; the device upload is a thin wrapper (upload_moe_row_adapter).