server.peers.subscribe is attacker-controlled data: ParsePeers assumed
the standard [ip, hostname, [features...]] shape and threw on anything
else (non-array response, wrong element types), and GetString() on a
JSON string containing invalid UTF-8 bytes threw InvalidOperationException
instead of failing to parse — both found by fuzzing. Any unexpected
shape or unparseable string now degrades to "no usable data" instead of
propagating an exception into the sync/discovery path.