Fix node-facts.sh bugs and add stub-curl integration tests

- Fix grep -qE calls to handle variables starting with '-' (add -- separator)
- Remove local declarations at top level by wrapping main body in main() function
- Replace bounded-worker scheduler with simpler temp file + wait -n pattern
- Fix per-node fan-out to capture function output instead of re-calling
- Add stub-curl integration tests that catch all three original issues
- Add fixture compose files for avalanche, op-node+beacon, geth testing
- Update test path-blacklist.txt to include entry starting with -

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

node-facts-test/ethereum-mainnet-lighthouse.yml

@@ -0,0 +1,11 @@
+version: "3"
+services:
+  client:
+    image: sigp/lighthouse:v5.3.0
+    labels:
+      - "traefik.http.routers.ethereum-mainnet-lighthouse.rule=PathPrefix(`/ethereum-mainnet-lighthouse`)"
+      - "traefik.http.middlewares.ethereum-mainnet-lighthouse.stripprefix.prefixes=/ethereum-mainnet-lighthouse"
+    x-upstreams:
+      network: ethereum
+      chain: ethereum-mainnet
+chain: ethereum-mainnet