feat: ix_moe_bridge + ix_attn_bridge — dlopen bridges for full ixformer::infer API

Bridge architecture (from xllm/core/kernels/ilu/ixformer.h):

ix_moe_bridge.so (MoE 7-step fused pipeline):
  - topk_softmax → moe_compute_token_index_api → moe_expand_input
  - moe_w16a16_group_gemm (x2) → silu_and_mul → moe_output_reduce_sum
  - fused_moe_forward(): replaces entire Python expert loop
  - Fix: group_gemm format NT→TN (match xllm trans_b=true)

ix_attn_bridge.so (attention + linear):
  - ixinfer_flash_attn_unpad_with_block_tables (fused prefill)
  - xllm_paged_attention (fused paged decode)
  - ixformer_linear (matmul + activation)
  - residual_rms_norm (fused residual + norm)

Integration:
  - ix_fused_moe.py: Python loader (prebuilt .so → JIT → unavailable)
  - qwen3_5.py: Tier 0 dispatch in _pure_pytorch_experts()
  - patch_ops.sh: deploys ix_fused_moe.py + all prebuilt/*.so

Source: jd-opensource/xllm (fresh clone, all ILU kernels verified SAME)
Sync: upstream_ref/xllm_latest/models/llm/qwen3_next_hybrid_base.h (+32 lines)

Build on real machine:
  bash qwen3_6_scripts/build_ix_moe_bridge.sh
  bash qwen3_6_scripts/build_ix_attn_bridge.sh

qwen3_6_scripts/build_ix_moe_bridge.sh

@@ -0,0 +1,84 @@
+#!/bin/bash
+# build_ix_moe_bridge.sh — Build ix_moe_bridge.so on real BI-V100
+#
+# This compiles ex_engine/csrc/ix_moe_bridge.cpp into a prebuilt .so
+# that can be deployed without JIT compilation in Docker.
+#
+# Run on real machine: bash qwen3_6_scripts/build_ix_moe_bridge.sh
+# Output: qwen3_6_scripts/prebuilt/corex-3.2.3-ivcore10/ix_moe_bridge.so
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+PROJECT_DIR="$(dirname "$SCRIPT_DIR")"
+CPP_SOURCE="${PROJECT_DIR}/ex_engine/csrc/ix_moe_bridge.cpp"
+PREBUILT_DIR="${SCRIPT_DIR}/prebuilt/corex-3.2.3-ivcore10"
+
+if [ ! -f "$CPP_SOURCE" ]; then
+    # Also try the local copy
+    CPP_SOURCE="${SCRIPT_DIR}/ix_moe_bridge.cpp"
+fi
+
+if [ ! -f "$CPP_SOURCE" ]; then
+    echo "ERROR: ix_moe_bridge.cpp not found"
+    exit 1
+fi
+
+echo "=== Building ix_moe_bridge.so ==="
+echo "Source: $CPP_SOURCE"
+echo "Output: $PREBUILT_DIR/ix_moe_bridge.so"
+
+python3 -c "
+import os, sys, glob
+from torch.utils.cpp_extension import load
+
+cpp_source = '$CPP_SOURCE'
+extra_ldflags = []
+
+# Find ixformer .so to link against
+try:
+    import ixformer
+    ixf_dir = os.path.dirname(ixformer.__file__)
+    for so in glob.glob(os.path.join(ixf_dir, '*.so')):
+        extra_ldflags.append(so)
+    extra_ldflags.append(f'-Wl,-rpath,{ixf_dir}')
+except ImportError:
+    pass
+
+corex_lib = '/usr/local/corex/lib64'
+if os.path.isdir(corex_lib):
+    for lib in ['libixattn.so', 'libixformer.so', 'libcublas.so']:
+        p = os.path.join(corex_lib, lib)
+        if os.path.isfile(p):
+            extra_ldflags.append(p)
+    extra_ldflags.append(f'-Wl,-rpath,{corex_lib}')
+
+print(f'Linking: {extra_ldflags}')
+
+mod = load(
+    name='ix_moe_bridge',
+    sources=[cpp_source],
+    extra_cflags=['-O2', '-std=c++17'],
+    extra_ldflags=extra_ldflags,
+    verbose=True,
+)
+
+# Find the compiled .so and copy to prebuilt
+import torch.utils.cpp_extension as ext
+build_dir = ext._get_build_directory('ix_moe_bridge', verbose=False)
+print(f'Build dir: {build_dir}')
+
+import shutil
+for f in glob.glob(os.path.join(build_dir, '*.so')):
+    dst = '$PREBUILT_DIR/ix_moe_bridge.so'
+    os.makedirs(os.path.dirname(dst), exist_ok=True)
+    shutil.copy2(f, dst)
+    sz = os.path.getsize(dst)
+    print(f'✓ ix_moe_bridge.so ({sz} bytes) → {dst}')
+    break
+
+# Verify
+fns = [x for x in dir(mod) if not x.startswith('_')]
+print(f'Functions: {fns}')
+print('=== Build SUCCESS ===')
+"