feat: 10-file MoE bridge pipeline — compile, dispatch, patch, test

The complete chain to replace 180 Python fallback calls/token with C++:

BUILD:
  1. moe_ops_impl.cu (489L) — 5 MoE functions in ixformer::infer namespace
     - topk_softmax: dynamic num_experts (128 for Qwen3.5), shared-mem
     - moe_compute_token_index: histogram + prefix_sum + scatter
     - moe_expand_input: gather kernel
     - moe_w16a16_group_gemm: per-expert cuinferCustomGemm loop
     - moe_output_reduce_sum: weighted combine
  2. ix_full_bridge_v2.cpp (461L) — pybind11 bridge, 14+1 functions
  3. build_moe_bridge.sh — torch.utils.cpp_extension compile, link cuinfer+ixformer

DISPATCH:
  4. moe_dispatch.py — 3-tier fallback (fused → individual → PyTorch)
  5. patch_moe_hot_path.py — monkey-patch Qwen3_5MoE.forward()

CONFIG:
  6. computility-run.yaml — max_num_seqs 1→2 (match sub168 baseline)
  7. patch_ops.sh — add build + deploy steps for MoE bridge

VERIFY:
  8. probe_moe_symbols.sh — nm -D .so to confirm 5 MoE symbols present
  9. test_moe_bridge.py — random-tensor integration test (no weights needed)

DEPLOY:
 10. Dockerfile — COPY ex_engine sources for in-container compilation

ex_engine/python/patch_moe_hot_path.py

@@ -0,0 +1,109 @@
+"""patch_moe_hot_path.py — Replace Qwen3_5MoE.forward() with bridge dispatch.
+
+This is the key performance patch: replaces the Python expert-loop MoE
+with a single C++ call that does all 7 steps fused.
+
+Called by: patch_ops.sh during Docker build
+Target:    vllm.model_executor.models.qwen3_5.Qwen3_5MoE
+
+Reference: ex_engine/python/patch_vllm_hot_path.py (200L)
+"""
+import sys
+import logging
+import torch
+
+logger = logging.getLogger("patch_moe_hot_path")
+
+
+def apply_moe_patch():
+    """Monkey-patch Qwen3_5MoE.forward to use moe_dispatch."""
+    try:
+        from ex_engine.python.moe_dispatch import moe_forward, get_tier
+    except ImportError:
+        try:
+            from moe_dispatch import moe_forward, get_tier
+        except ImportError:
+            logger.warning("[moe_patch] moe_dispatch not available, skipping patch")
+            return False
+
+    tier = get_tier()
+    logger.info(f"[moe_patch] moe_dispatch tier={tier}")
+
+    # Find the MoE class
+    moe_cls = None
+    try:
+        from vllm.model_executor.models.qwen3_5 import Qwen3_5MoE
+        moe_cls = Qwen3_5MoE
+    except ImportError:
+        pass
+
+    if moe_cls is None:
+        # Try to find it in sys.modules (may be registered under different name)
+        for mod_name, mod in sys.modules.items():
+            if hasattr(mod, 'Qwen3_5MoE'):
+                moe_cls = getattr(mod, 'Qwen3_5MoE')
+                break
+
+    if moe_cls is None:
+        logger.warning("[moe_patch] Qwen3_5MoE class not found")
+        return False
+
+    # Save original forward
+    _original_forward = moe_cls.forward
+
+    def patched_forward(self, hidden_states, *args, **kwargs):
+        """Patched MoE forward using bridge dispatch."""
+        # Get router logits
+        # In Qwen3_5, the gate + shared_expert_gate are concatenated:
+        #   router_and_shared_gate = self.gate(hidden_states)
+        #   router_logits = router_and_shared_gate[..., :self.num_experts]
+        #   shared_gate = router_and_shared_gate[..., -1]
+        router_and_shared_gate = self.gate(hidden_states)
+        router_logits = router_and_shared_gate[..., :self.num_experts]
+
+        # Shared expert (if any) — run in parallel
+        shared_output = None
+        if hasattr(self, 'shared_expert') and self.shared_expert is not None:
+            if hasattr(self, 'shared_expert_gate'):
+                shared_gate = torch.sigmoid(
+                    router_and_shared_gate[..., -1].unsqueeze(-1))
+            else:
+                shared_gate = None
+
+        # Routed experts via bridge
+        try:
+            routed_output = moe_forward(
+                hidden_states.view(-1, hidden_states.shape[-1]),
+                router_logits.view(-1, router_logits.shape[-1]),
+                self.w13_weight if hasattr(self, 'w13_weight') else self.experts.w13_weight,
+                self.w2_weight if hasattr(self, 'w2_weight') else self.experts.w2_weight,
+                topk=self.top_k,
+                num_experts=self.num_experts,
+                renormalize=True,
+            )
+            routed_output = routed_output.view_as(hidden_states)
+        except Exception as e:
+            logger.warning(f"[moe_patch] Bridge failed ({e}), using original forward")
+            return _original_forward(self, hidden_states, *args, **kwargs)
+
+        # Add shared expert output
+        if hasattr(self, 'shared_expert') and self.shared_expert is not None:
+            shared_out = self.shared_expert(hidden_states)
+            if shared_gate is not None:
+                shared_out = shared_out * shared_gate
+            routed_output = routed_output + shared_out
+
+        return routed_output
+
+    # Only patch if we have a real bridge (not pure Python fallback)
+    if tier < 2:
+        moe_cls.forward = patched_forward
+        logger.info(f"[moe_patch] ✓ Patched Qwen3_5MoE.forward (tier={tier})")
+        return True
+    else:
+        logger.info("[moe_patch] Tier 2 (Python only), not patching")
+        return False
+
+
+if __name__ == "__main__":
+    apply_moe_patch()