Function resolve_moe_lora_route 

pub fn resolve_moe_lora_route(
    adapter_slot: i32,
    active: i32,
    has_moe_lora: bool,
) -> MoeLoraRoute

2026-09-25: The MoE LoRA fold decision for one request:

• !has_moe_lora ⇒ Fold;
• adapter_slot < 0 (base request) ⇒ Skip;
• adapter_slot == active ⇒ Fold;
• any other slot ⇒ Refuse, since only the active adapter is installed.

Model-engine’s moe_lora_route passes has_moe_lora = “a LoRA pool is loaded” and active = -1 when none is.