fix: Default tier back to Dense-first (MoE overheating at 91°C)

Heavy tier keeps MoE primary (workhorse for >25K tok).
Default tier routes Dense → VLM → MoE to prevent MoE overload.
MoE had 5 timeouts in 15 min when Default pushed overflow to it.

router/router.py

@@ -239,8 +239,8 @@ def route(rd, tier):
         result = select_best_gpu(candidates, "heavy_reasoning")
         if result: return result
     
-    # TIER 5: Default — MoE primary, Dense fallback
-    candidates = [m for m in ["qwen3.6-35B-A3B","qwen3.6-27B-code","qwen3.5-9b-vlm"] if m in avail]
+    # TIER 5: Default — Dense primary, MoE fallback
+    candidates = [m for m in ["qwen3.6-27B-code","qwen3.5-9b-vlm","qwen3.6-35B-A3B"] if m in avail]
     result = select_best_gpu(candidates, "default")
     if result: return result
     return {"model":avail[0],"reason":"last_resort"}