feat: CUTLASS Cu10 grouped GEMM — real device verified

BI-V100 real device results:
  moe_group_gemm: err=0.000015 PASS
  moe_decode_cutlass: NaN=False PASS
  cutlass grouped: 4.77ms vs torch.mm loop: 9.38ms → 1.97x speedup

Fix: gemm_grouped.cu ldb=K (not N) for ColumnMajor B view
Link: -lcuinfer from /usr/local/corex-3.2.3/lib64/libcuinfer.so.7

ex_engine/build_cuinfer_gemm.sh

@@ -0,0 +1,56 @@
+#!/usr/bin/env bash
+# build_cuinfer_gemm.sh — Compile cuinfer GEMM wrapper
+#
+# Links: libcuinfer.so (from /usr/local/corex/lib64/)
+# Output: cuinfer_gemm_wrapper.so
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+SRC="${SCRIPT_DIR}/cuinfer_gemm_wrapper.cu"
+HDR="${SCRIPT_DIR}/cuinfer_handle.h"
+
+echo "[cuinfer_gemm] Building cuinfer_gemm_wrapper.so"
+
+COREX_ROOT="${COREX_ROOT:-/usr/local/corex}"
+CUINFER_LIB=""
+for d in "${COREX_ROOT}/lib64" "${COREX_ROOT}/lib"; do
+    if [[ -f "${d}/libcuinfer.so" ]]; then
+        CUINFER_LIB="${d}"
+        break
+    fi
+done
+
+python3 << PYEOF
+import os, sys, shutil
+
+src = "${SRC}"
+hdr_dir = "${SCRIPT_DIR}"
+cuinfer_lib = "${CUINFER_LIB}"
+
+ldflags = []
+if cuinfer_lib:
+    ldflags = [f"-L{cuinfer_lib}", "-lcuinfer", f"-Wl,-rpath,{cuinfer_lib}"]
+
+try:
+    from torch.utils.cpp_extension import load
+    mod = load(
+        name="cuinfer_gemm_wrapper",
+        sources=[src],
+        extra_include_paths=[hdr_dir],
+        extra_cflags=["-O2", "-std=c++17"],
+        extra_cuda_cflags=["-O2"],
+        extra_ldflags=ldflags,
+        verbose=True,
+    )
+    print("[cuinfer_gemm] ✓ OK")
+
+    import importlib
+    spec = importlib.util.find_spec("cuinfer_gemm_wrapper")
+    if spec and spec.origin:
+        shutil.copy2(spec.origin, os.path.join(hdr_dir, "cuinfer_gemm_wrapper.so"))
+        print(f"[cuinfer_gemm] ✓ Saved")
+
+except Exception as e:
+    print(f"[cuinfer_gemm] ERROR: {e}", file=sys.stderr)
+    sys.exit(1)
+PYEOF