feat: sync ephemeral transient messages

Sync telesrv 570ccf8 (feat(ephemeral): implement Layer 228 transient messages).

Skipped telesrv docs changes per public sync rules; normalized the public appearance seed label.

internal/rpc/users_bot_info_test.go

@@ -0,0 +1,25 @@
+package rpc
+
+import (
+	"testing"
+
+	"telesrv/internal/domain"
+)
+
+func TestTGBotInfoPreservesEphemeralCommandMarker(t *testing.T) {
+	got := tgBotInfoFromProfile(42, domain.BotProfile{
+		Commands: []domain.BotCommand{
+			{Command: "public", Description: "visible everywhere"},
+			{Command: "private", Description: "Layer 228 only", Ephemeral: true},
+		},
+	}, true)
+	if len(got.Commands) != 2 {
+		t.Fatalf("commands = %+v, want two", got.Commands)
+	}
+	if got.Commands[0].Ephemeral {
+		t.Fatalf("public command = %+v, want ephemeral=false", got.Commands[0])
+	}
+	if !got.Commands[1].Ephemeral {
+		t.Fatalf("private command = %+v, want ephemeral=true", got.Commands[1])
+	}
+}