perf(comms): alarms-only seed, capped buffers, at-least-once audit pull

src/ZB.MOM.WW.ScadaBridge.Communication/Protos/site_command.proto

@@ -553,6 +553,14 @@ message EventLogQueryResponseDto {
 message DebugSnapshotRequestDto {
   string instance_unique_name = 1;
   string correlation_id = 2;
+  // Alarms-only projection (WP2.3 wire efficiency): when true the site builds
+  // and returns ONLY the alarm rows of the debug snapshot, leaving
+  // attribute_values empty. Used by the central per-site live alarm cache,
+  // whose seed/reconcile fan-out discards every attribute row anyway — a full
+  // snapshot ships the whole attribute surface of every enabled instance once
+  // per reconcile for nothing. proto3 defaults it to false, so an older
+  // central that never sets it keeps the full-snapshot behaviour. Additive-only.
+  bool alarms_only = 3;
 }
 
 message SubscribeDebugViewRequestDto {