fix: adapt xllm norm.cu for corex CUB (CUDA 10.2)

Key change: replace CCCL 3.6 types with corex CUB equivalents
  - cuda::std::plus<> → cub::Sum
  - cuda::maximum<>  → cub::Max
  - Remove #include <cuda/std/functional>

Test results from real machine (3/4 passed):
  ✓ __shfl_down_sync works on ivcore10
  ✓ manual SMEM+shuffle block reduce works
  ✓ corex CUB cub::BlockReduce<float,256> compiles and runs correctly (32640)
  ✗ CCCL 3.6 variadic function issue — corex clang rejects device variadic

Confirmed: use /usr/local/corex/include/cub/ for all kernel code
           cccl_upstream is reference only, NOT compilable on corex

Build script: bash qwen3_6_scripts/build_xllm_kernels.sh

qwen3_6_scripts/build_xllm_kernels.sh

@@ -0,0 +1,61 @@
+#!/bin/bash
+# build_xllm_kernels.sh — Compile xllm CUDA kernels into .so on BI-V100
+#
+# Uses corex's own CUB (/usr/local/corex/include/cub/) NOT cccl_upstream
+# Source: ex_engine/xllm_kernels/cuda/
+# Output: qwen3_6_scripts/prebuilt/corex-3.2.3-ivcore10/
+#
+# Run: bash qwen3_6_scripts/build_xllm_kernels.sh
+
+set -euo pipefail
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+PROJECT_DIR="$(dirname "$SCRIPT_DIR")"
+CUDA_DIR="${PROJECT_DIR}/ex_engine/xllm_kernels/cuda"
+HEADER_DIR="${CUDA_DIR}/headers"
+PREBUILT_DIR="${SCRIPT_DIR}/prebuilt/corex-3.2.3-ivcore10"
+mkdir -p "$PREBUILT_DIR"
+
+build_kernel() {
+    local name="$1"
+    local cu_file="$2"
+    echo "=== Building ${name}.so ==="
+    python3 -c "
+import os, glob, shutil
+from torch.utils.cpp_extension import load
+
+mod = load(
+    name='${name}',
+    sources=['${cu_file}'],
+    extra_cflags=['-std=c++17'],
+    extra_include_paths=['${HEADER_DIR}', '/usr/local/corex/include'],
+    verbose=True,
+)
+
+import torch.utils.cpp_extension as ext
+build_dir = ext._get_build_directory('${name}', verbose=False)
+for f in glob.glob(os.path.join(build_dir, '*.so')):
+    dst = '${PREBUILT_DIR}/${name}.so'
+    shutil.copy2(f, dst)
+    sz = os.path.getsize(dst)
+    print(f'✓ ${name}.so ({sz} bytes) → {dst}')
+    break
+
+fns = [x for x in dir(mod) if not x.startswith('_')]
+print(f'Functions: {fns}')
+"
+}
+
+echo "Building xllm CUDA kernels for BI-V100 (ivcore10)"
+echo "Using corex CUB: /usr/local/corex/include/cub/"
+echo ""
+
+# Build each kernel
+build_kernel "xllm_norm"       "${CUDA_DIR}/norm.cu"
+build_kernel "xllm_activation" "${CUDA_DIR}/activation.cu"
+build_kernel "xllm_rope"       "${CUDA_DIR}/rope.cu"
+build_kernel "xllm_block_copy" "${CUDA_DIR}/block_copy.cu"
+build_kernel "xllm_cache"      "${CUDA_DIR}/reshape_paged_cache.cu"
+
+echo ""
+echo "=== All kernels built ==="
+ls -la "${PREBUILT_DIR}"/xllm_*.so 2>/dev/null