update proto, add config update publish broadcast, add messages compacting

flatbuffers/compacted.fbs

@@ -0,0 +1,12 @@
+namespace hmmmm;
+
+// A single serialized ServerMessage frame packed into a byte vector.
+table CompactedFrame {
+    data: [ubyte];
+}
+
+// A batch of ServerMessage frames sent as a single WebSocket frame to reduce
+// per-frame syscall overhead when message rate exceeds the batching threshold.
+table CompactedMessage {
+    frames: [CompactedFrame];
+}