fix(telegram): reopen a deleted support topic instead of losing it to General

Telegram silently routes a copyMessage aimed at a deleted forum topic
into the chat's General topic with NO error, so the bot's error-based
recreate never fired — the user's next message landed in General with no
card. Confirmed against the prod bot logs: a relay after a topic deletion
logged neither "relay to topic failed" nor "topic gone, reopening".

Probe topic liveness before reusing it: re-applying the info card's reply
markup is a no-op that errors only when the card (hence the topic) is
gone, so the bot detects the deletion and reopens the topic + card rather
than relying on the (absent) copy error. The post-copy recreate stays as
a race backstop.

platform/telegram/internal/bot/support_test.go

@@ -38,6 +38,9 @@ type supportAPI struct {
 	deleted      [][]int
 	editedMsgIDs []string
 	answers      []string
+	// editErr, when set, makes editMessageReplyMarkup return that Telegram error
+	// description (simulating a deleted info card / topic).
+	editErr string
 }
 
 func newSupportAPI(adminIDs ...int64) *supportAPI {
@@ -77,6 +80,10 @@ func (s *supportAPI) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		s.deleted = append(s.deleted, ids)
 		io.WriteString(w, `{"ok":true,"result":true}`)
 	case strings.HasSuffix(path, "/editMessageReplyMarkup"):
+		if s.editErr != "" {
+			fmt.Fprintf(w, `{"ok":false,"error_code":400,"description":%q}`, s.editErr)
+			return
+		}
 		s.editedMsgIDs = append(s.editedMsgIDs, r.FormValue("message_id"))
 		io.WriteString(w, `{"ok":true,"result":{"message_id":1}}`)
 	case strings.HasSuffix(path, "/answerCallbackQuery"):
@@ -181,6 +188,36 @@ func TestSupportSubsequentReusesTopic(t *testing.T) {
 	}
 }
 
+// TestSupportTopicRecreatedWhenDeleted covers the case the operator hit in prod:
+// after they delete a user's whole topic, Telegram routes a copy aimed at it into
+// General with no error, so the bot must proactively detect the dead topic (the card
+// probe fails) and reopen it instead of silently losing the message to General.
+func TestSupportTopicRecreatedWhenDeleted(t *testing.T) {
+	api := newSupportAPI()
+	api.editErr = "message to edit not found" // the operators deleted the topic + its card
+	b, st := newSupportBot(t, api)
+	// Seed a topic that has since been deleted in Telegram.
+	if err := st.SetTopic(7, 999, 4999, "Ann", "", "annlee"); err != nil {
+		t.Fatalf("seed topic: %v", err)
+	}
+
+	b.handleSupportUserMessage(context.Background(), userMsg(7, "still there?"))
+
+	if api.topicsOpened != 1 {
+		t.Fatalf("topics opened = %d, want 1 (reopened after deletion)", api.topicsOpened)
+	}
+	rec, _ := st.Get(7)
+	if rec.TopicID != 1000 || rec.HeaderMsgID != 5000 {
+		t.Errorf("store = topic %d / header %d, want the reopened 1000 / 5000", rec.TopicID, rec.HeaderMsgID)
+	}
+	if len(api.copies) != 1 || api.copies[0].threadID != "1000" {
+		t.Errorf("relay copies = %+v, want one into the reopened topic 1000", api.copies)
+	}
+	if _, ok := st.ByTopic(999); ok {
+		t.Error("stale topic 999 still indexed after reopen")
+	}
+}
+
 func TestSupportBlockedUserDropped(t *testing.T) {
 	api := newSupportAPI()
 	b, st := newSupportBot(t, api)