Function select_routed_pair 

pub fn select_routed_pair(
    layers: &[Option<LoraLayerWeights>],
    global_layer_idx: usize,
    module: LoraModule,
) -> Option<&LoraPair>

#30 (routed-prefill precision): pure selector for a routed prefill’s (global_layer, module) LoraPair out of a request slot’s GLOBAL-layer-indexed layers. None when the index is out of range, the layer is unadapted, or the routed adapter does not adapt that module (the caller then falls back to the bgmv/installed path — no delta if the slot’s a_table cell is base). GPU-free + unit-tested so the (layer, module) indexing is verifiable without hardware.