op-stack EL: publish p2p port + keep discovery on for node_sync nodes (49 composes)

Operator decision 2026-10-04 (sebastian): consensus-layer-synced op-stack nodes used to run
with --nodiscover / --disable-discovery and no published p2p port. A 0-peer EL can never
backfill a dropped-gossip gap, so op-node wedges in FCU-SYNCING until L1 derivation
catches up (katana 09-19..26, zircuit, mode). Blocks still arrive only via op-node; EL
peers are for gap-fill. Our own copies now discover each other implicitly.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RzxemENdcZBCxdGrzXiFvS

op/geth/bob-sepolia-op-geth-pruned-pebble-path.yml

@@ -45,6 +45,9 @@ services:
     ulimits:
       nofile: 1048576    # Max open files (for RPC/WS connections)
     user: root
+    ports:
+      - 13979:13979
+      - 13979:13979/udp
     expose:
       - 8545
       - 6060
@@ -61,8 +64,9 @@ services:
       - --metrics
       - --metrics.addr=0.0.0.0
       - --metrics.port=6060
+      - --nat=extip:${IP}
       - --networkid=808813
-      - --nodiscover
+      - --port=13979
       - --rpc.gascap=600000000
       - --rpc.txfeecap=0
       - --state.scheme=path