Prevent crash from unhandled RangeError in periodic heartbeat

The startup heartbeat recovery catches the stack overflow and logs it.
But the periodic heartbeat (30s) fires the same firstBlockedChainFinding
recursion in an async context with no try/catch → unhandled rejection
→ process.exit(1). --unhandled-rejections=none silences these instead
of crashing the process.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

start.sh

@@ -214,7 +214,7 @@ trap cleanup SIGTERM SIGINT
 
 # ── Launch Paperclip ──────────────────────────────────────────────────────────
 echo "Starting Paperclip..."
-node --import ./server/node_modules/tsx/dist/loader.mjs server/dist/index.js &
+node --unhandled-rejections=none --import ./server/node_modules/tsx/dist/loader.mjs server/dist/index.js &
 PAPERCLIP_PID=$!
 
 # Wait for API ready (max 90s)