fix: claude subprocess not killed on INT/TERM in cleanup trap (#530)

Track CLAUDE_PID before launching the claude subprocess so cleanup()
can kill it before reverting Anvil state. Running claude via `&` +
`wait` lets the trap fire immediately on INT/TERM, killing the
subprocess and preventing it from making calls against an
already-reverted chain.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/harb-evaluator/red-team.sh

@@ -180,8 +180,12 @@ SNAP=$("$CAST" rpc anvil_snapshot --rpc-url "$RPC_URL" | tr -d '"')
 log "  Snapshot ID: $SNAP"
 
 # Revert to the baseline snapshot on exit so subsequent runs start clean.
+CLAUDE_PID=""
 cleanup() {
   local rc=$?
+  if [[ -n "${CLAUDE_PID:-}" ]]; then
+    kill "$CLAUDE_PID" 2>/dev/null || true
+  fi
   if [[ -n "${SNAP:-}" ]]; then
     "$CAST" rpc anvil_revert "$SNAP" --rpc-url "$RPC_URL" >/dev/null 2>&1 || true
   fi
@@ -661,8 +665,11 @@ set +e
 # omitting it causes the CLI to exit with an error, producing an empty stream log.
 timeout "$CLAUDE_TIMEOUT" claude -p --dangerously-skip-permissions \
   --verbose --output-format stream-json \
-  "$PROMPT" >"$STREAM_LOG" 2>&1
+  "$PROMPT" >"$STREAM_LOG" 2>&1 &
+CLAUDE_PID=$!
+wait "$CLAUDE_PID"
 AGENT_EXIT=$?
+CLAUDE_PID=""
 set -e
 
 if [[ $AGENT_EXIT -ne 0 ]]; then