fix(check-health): retry on unreachable reference endpoint

When multicurl fails to reach the reference RPC (timeout/unreachable),
clean up the temp file, retry up to MAX_RETRIES, then exit with
'unverified (reference unreachable)' instead of falling through as success.

Also add Robinhood mainnet official RPC to reference-rpc-endpoint.json.

Co-authored-by: Cursor <cursoragent@cursor.com>

check-health.sh

@@ -380,6 +380,14 @@ if [ $? -eq 0 ]; then
 		    echo "unverified ($http_status_code2)"
 		    exit 1
                 fi 
+            else
+                rm "$response_file2"
+                if [ $attempt -lt $MAX_RETRIES ]; then
+                    attempt=$((attempt + 1))
+                    continue
+                fi
+                echo "unverified (reference unreachable)"
+                exit 1
             fi
             done
             

reference-rpc-endpoint.json

@@ -3394,6 +3394,7 @@
     "lagging_lag": 20,
     "syncing_lag": 40,
     "urls": [
+      "https://rpc.mainnet.chain.robinhood.com",
       "https://robinhood.drpc.org"
     ]
   },