bench.sh: add trap for graceful cleanup on kill/interrupt

Added EXIT/INT/TERM traps to ensure vLLM, proxy, and gpu_monitor
processes are cleaned up even when bench.sh is killed externally.
Also includes gpu_monitor in cleanup_gpu pattern matching.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

scripts/bench.sh

@@ -87,12 +87,11 @@ CONF
 # ─── GPU Cleanup (verified) ────────────────────────────────────────────────
 
 cleanup_gpu() {
-    echo "[cleanup] Killing all vLLM/proxy processes..."
-    for p in $(ps aux | grep -E 'vllm serve|cache_aware_proxy' | grep -v grep | awk '{print $2}' 2>/dev/null); do
+    echo "[cleanup] Killing all vLLM/proxy/monitor processes..."
+    for p in $(ps aux | grep -E 'vllm serve|cache_aware_proxy|gpu_monitor' | grep -v grep | awk '{print $2}' 2>/dev/null); do
         kill -9 "$p" 2>/dev/null || true
     done
     sleep 3
-    # Kill any remaining GPU holders
     local gpu_pids
     gpu_pids=$(fuser /dev/nvidia* 2>/dev/null | tr ' ' '\n' | sort -u | grep -v '^$' || true)
     if [ -n "$gpu_pids" ]; then
@@ -100,7 +99,6 @@ cleanup_gpu() {
         echo "$gpu_pids" | xargs -r kill -9 2>/dev/null || true
         sleep 5
     fi
-    # Verify GPUs are free
     local used
     used=$(nvidia-smi --query-gpu=memory.used --format=csv,noheader,nounits 2>/dev/null | awk '{s+=$1} END{print s}')
     if [ "${used:-0}" -gt 100 ]; then
@@ -111,6 +109,9 @@ cleanup_gpu() {
     echo "[cleanup] All GPUs verified free."
 }
 
+trap 'echo "[bench.sh] Caught signal, cleaning up..."; cleanup_gpu; exit 1' INT TERM
+trap 'cleanup_gpu' EXIT
+
 # ─── Launch vLLM instances ─────────────────────────────────────────────────
 
 launch_instances() {
@@ -335,6 +336,6 @@ launch_proxy
 run_benchmark
 collect_artifacts
 print_summary
-cleanup_gpu
+# cleanup_gpu runs automatically via EXIT trap
 
 echo "[done] $(date)"