fix(interface): corex_moe accepts w13 merged format + no silent fallback

corex_moe.py: moe_forward now accepts both formats:
  Format A: w1(E,I,H) + w2(E,H,I) + w3(E,I,H) — xllm style, separate gate/up
  Format B: w13(E,2*I,H) + w2(E,H,I) + w3=None — vllm style, merged gate_up
  Auto-detects by checking if w3 is None, splits w13 internally.

qwen3_5.py:
  - Fix corex_moe call: use keyword args (w3=None, topk=self.top_k)
    prevents topk integer going to w3 tensor position
  - Remove silent fallback on corex_moe failure — raise RuntimeError
    with full shape info for diagnosis. Zero score with no error log
    is worse than a crash.

qwen3_6_scripts/qwen3_5.py

@@ -1207,12 +1207,16 @@ class Qwen3_5MoeSparseBlock(nn.Module):
                 routed_out = self._corex_moe_forward(
                     hidden_states, router_logits,
                     self.experts.w13_weight, self.experts.w2_weight,
-                    self.top_k,
+                    w3=None, topk=self.top_k,
                 )
             except Exception as e:
-                logger.warning("CoreX MoE forward failed (%s), falling back permanently", e)
-                self._use_corex_moe = False
-                routed_out = self._pure_pytorch_experts(hidden_states, router_logits)
+                # NO FALLBACK — crash with error log so we can diagnose
+                logger.error("CoreX MoE forward FAILED: %s", e)
+                raise RuntimeError(
+                    f"corex_moe.moe_forward failed: {e}. "
+                    f"Shapes: hidden={hidden_states.shape}, router={router_logits.shape}, "
+                    f"w13={self.experts.w13_weight.shape}, w2={self.experts.w2_weight.shape}"
+                ) from e
         else:
             routed_out = self._pure_pytorch_experts(hidden_states, router_logits)