docs: add node healthcheck runbook

docs/HEALTHCHECK_RUNBOOK.md

@@ -0,0 +1,45 @@
+# Node Healthcheck Runbook
+
+This runbook provides quick checks to validate your node is healthy.
+
+1) Containers are up
+
+Run:
+  docker compose ps
+
+You should see expected services in running state.
+
+2) Logs show progress (no loops)
+
+Run:
+  docker compose logs --since=10m --tail=200
+
+Look for:
+- steady block processing or syncing messages
+- no repeated crash or restart loops
+
+3) RPC answers
+
+Check block number from the execution endpoint by running:
+  curl -s -H "Content-Type: application/json" -d '{"jsonrpc":"2.0","method":"eth_blockNumber","params":[],"id":1}' http://localhost:8545
+
+A valid hex block number means the RPC endpoint is responsive.
+
+4) Disk space
+
+Run:
+  df -h
+  du -sh ./data 2>/dev/null || true
+
+Ensure there is enough free disk space and the data directory is not growing unexpectedly fast.
+
+5) Common quick fixes
+
+Restart services:
+  docker compose restart
+
+Pull latest images and restart:
+  docker compose pull
+  docker compose up -d
+
+If the node state looks corrupted, restore from a known-good snapshot following the official Base documentation.