chore(clients): roll out feed-level snapshot_status to all five clients

Task 1 added AlarmSnapshotStatus and AlarmFeedMessage.snapshot_status = 5.
Carry it downstream from the canonical Contracts protos:

- Rust vendored protos under clients/rust/protos, refreshed byte-identical
  (build.rs falls back to them for out-of-repo tarball builds)
- client descriptor set (protoc 34.1 pin)
- Go (protoc-gen-go v1.36.11 / protoc-gen-go-grpc 1.6.2)
- Python (grpcio-tools 1.80.0 pin)
- Java (gradle generateProto)

.NET needs no regeneration: the client compiles against the Contracts
Generated/ output committed with the proto change.

The hand-written CLI feed renderers switch on the payload oneof, so codegen
alone does not carry the arm. Add snapshot-status to the .NET, Go, Rust, and
Java renderers; the .NET and Go renderers were also missing provider-status,
which has been on the wire since the provider-mode work, so add it there too.
Java's renderer is an exhaustive switch expression and did not compile until
the new case landed. The Python CLI renders generic protobuf-JSON and needs
no change.

Each client README gains a paragraph on the feed-level frame next to its
existing from_truncated_snapshot paragraph: it arrives at stream open after
provider_status and before the cached active_alarm frames, then on every
verdict change including the clearing frame a monitor restart emits, so a
live consumer can track set completeness without polling QueryActiveAlarms.

GatewayDashboardDesign: list the two new payload cases the AlarmsHub forwards,
and — separately — record the GroupToRole / GroupToTag / UntaggedSessionVisibility
rows the settings page already renders but the bullet list omitted.

clients/go/cmd/mxgw-go/main.go

@@ -1097,7 +1097,8 @@ func runStreamAlarms(ctx context.Context, args []string, stdout, stderr io.Write
 
 // formatAlarmFeedMessage renders one AlarmFeedMessage in the CLI's plain-text
 // output style, distinguishing the active-alarm snapshot, snapshot-complete
-// sentinel, and transition cases of the message's payload oneof.
+// sentinel, transition, provider-status, and snapshot-status cases of the
+// message's payload oneof.
 func formatAlarmFeedMessage(message *mxgateway.AlarmFeedMessage) string {
 	switch {
 	case message.GetActiveAlarm() != nil:
@@ -1108,6 +1109,11 @@ func formatAlarmFeedMessage(message *mxgateway.AlarmFeedMessage) string {
 	case message.GetTransition() != nil:
 		transition := message.GetTransition()
 		return fmt.Sprintf("transition %s kind=%s severity=%d", transition.GetAlarmFullReference(), transition.GetTransitionKind(), transition.GetSeverity())
+	case message.GetProviderStatus() != nil:
+		status := message.GetProviderStatus()
+		return fmt.Sprintf("provider-status mode=%s degraded=%t reason=%q", status.GetMode(), status.GetDegraded(), status.GetReason())
+	case message.GetSnapshotStatus() != nil:
+		return fmt.Sprintf("snapshot-status truncated=%t", message.GetSnapshotStatus().GetTruncated())
 	default:
 		return "unknown"
 	}