fix(ui): сохранять явный выбор туннеля диагностики

app/(main)/probes/page.tsx

@@ -590,7 +590,7 @@ function ProbesContent() {
   const [traceUseDns, setTraceUseDns] = useState(false)
   const [traceHops]                  = useState(30)
   const [dnsType,    setDnsType]     = useState<DnsType>("A")
-  const [bwTunId,    setBwTunId]     = useState("")
+  const [bwChoice, setBwChoice] = useState<{ serverId: string; id: string } | null>(null)
   const [bwProto,    setBwProto]     = useState<"tcp" | "udp">("tcp")
   const [bwDuration, setBwDuration]  = useState(10)
   const [runBusy, setRunBusy]        = useState(false)
@@ -671,11 +671,6 @@ function ProbesContent() {
   }, [isLive, greByServer, srcId])
 
 
-  useEffect(() => {
-    const list = isLive ? (greByServer[srcId] ?? []) : greTunnels.filter(t => t.serverId === srcId)
-    if (list.length && !list.some(t => t.id === bwTunId)) setBwTunId(list[0]!.id)
-  }, [isLive, greByServer, srcId, bwTunId])
-
   // ── run state ──
   const [tests,   setTests]   = useState<DiagTest[]>([])
   const [tab,     setTab]     = useState<"history" | "schedule">("history")
@@ -694,6 +689,8 @@ function ProbesContent() {
   }, [])
 
   const bwTunnels = tunnelsForSrc
+  const bwTunId = bwChoice?.serverId === srcId ? bwChoice.id : (bwTunnels[0]?.id ?? "")
+  const setBwTunId = (id: string) => setBwChoice({ serverId: srcId, id })
   const srcServer = useMemo(() => allServers.find(s => s.id === srcId), [allServers, srcId])
   const sourceKey = JSON.stringify([srcId, srcServer?.host])
   const sourceRequired = tool === "ping" || tool === "traceroute" || tool === "mtu"
@@ -744,7 +741,7 @@ function ProbesContent() {
         target: tool === "bandwidth" ? (bwTun?.name ?? target) : target,
         command: cmdPreview,
         startedAt: Date.now(),
-        lines: [{ text: "Выполняется запрос к MikroTik через API…", kind: "dim" }],
+        lines: [{ text: tool === "dns" ? "Выполняется DNS-запрос приложения…" : "Выполняется запрос к MikroTik через API…", kind: "dim" }],
         totalLines: 1,
         source: "live",
       }, ...p.slice(0, 9)])
@@ -1014,7 +1011,8 @@ function ProbesContent() {
                 {tool === "bandwidth" && (
                   <div>
                     <OptionLabel>GRE-туннель (цель)</OptionLabel>
-                    <NativeSelect ariaLabel="GRE-туннель для BW-теста" value={bwTunId} onChange={setBwTunId} className="min-w-[180px]">
+                    <NativeSelect ariaLabel="GRE-туннель для BW-теста" value={bwTunnels.some(t => t.id === bwTunId) ? bwTunId : ""} onChange={setBwTunId} className="min-w-[180px]">
+                      {!bwTunnels.some(t => t.id === bwTunId) && <option value="" disabled>Выберите GRE-туннель</option>}
                       {bwTunnels.map(t => <option key={t.id} value={t.id}>{t.name}</option>)}
                     </NativeSelect>
                   </div>