monitoring scripts: protocol dispatch via registry slug + mantle/metis chainid fixes

- sync-status.sh: resolve protocol family from the compose x-upstreams chain
  label via the registry (reference-rpc-endpoint.sh --protocol) instead of
  path-substring guessing; legacy path detection kept as fallback for
  composes without a resolved label. Unknown families report
  'unsupported protocol: X' honestly instead of a bogus eth_chainId error.
  Aztec reference lookup falls back to slug urls when rollup_version is
  not in the registry.
- reference-rpc-endpoint.sh: new --chain <slug> (urls by registry key,
  works for idless non-EVM entries) and --protocol <slug> modes; existing
  chainid and --rollup-version lookups unchanged.
- mantle-sepolia: chainid 5001 -> 5003 (verified live: 0x138b), label and
  --networkid now correct
- metis-sepolia: label resolves via registry override (drpc chains.yaml
  carries wrong id 59901; live chain is 59902, verified via official RPC)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

reference-rpc-endpoint.json

@@ -472,7 +472,7 @@
   },
   "metis-sepolia": {
     "protocol": "eth",
-    "id": 59901,
+    "id": 59902,
     "urls": [
       "https://metis-sepolia.drpc.org"
     ]