feat(11-06): add the tide fake Centrifugo recorder, broadcast goldens and parity:broadcasts

- CentrifugoRecorder records publish/broadcast requests (method, path,
  whether the API key matched, JSON body) and binds loopback only
- BroadcastGolden load/write, NormalizePublications (timestamps, actor,
  captured ids only) and DiffPublications (structural, key order ignored)
- RecordBroadcasts runs a flow or one step against a loopback backend
- summer parity:broadcasts wraps it; README documents format and rules

cmd/summer/main.go

@@ -38,6 +38,7 @@ func toolCommands() []bonfire.Command {
 		parityProxyCommand(),
 		parityRecordCommand(),
 		parityReplayCommand(),
+		parityBroadcastsCommand(),
 		delegateCommand("migrate", "Run plugin migrations in the app binary"),
 		delegateRollbackCommand(),
 		delegateCommand("migrate:status", "Show per-plugin migration history in the app binary"),