fix(telegram): support card — text_mention name, no command/dead link

The topic info card built the profile link as `tg://user?id=`, which
clients render as dead text for a user they don't already know (the
test-vs-prod difference an operator saw), and it put the raw display
name through HTML — so a name starting with "/" was auto-detected as a
tappable bot command that fired when tapped.

Render the card with message entities instead: the display name is
covered by a `text_mention` entity (the reliable way to mention a
username-less user the bot has already seen — it messaged the bot),
which links the profile AND, because the name sits inside an entity,
suppresses the "/command" and "@mention" auto-detection on it. Drop the
HTML parse mode and the tg:// link. Entity offsets are UTF-16.

platform/telegram/internal/bot/support_test.go

@@ -360,21 +360,53 @@ func TestParseSupportCallback(t *testing.T) {
 	}
 }
 
-func TestSupportCardTextEscapes(t *testing.T) {
-	u := &models.User{ID: 7, FirstName: "<b>Ann</b>", Username: "ann", LanguageCode: "ru", IsPremium: true}
-	card := supportCardText(u)
-	if strings.Contains(card, "<b>Ann</b>") {
-		t.Error("user-supplied first name was not HTML-escaped in the card")
-	}
-	if !strings.Contains(card, "&lt;b&gt;Ann&lt;/b&gt;") {
-		t.Errorf("card = %q, want the escaped name", card)
-	}
-	if !strings.Contains(card, "tg://user?id=7") {
-		t.Error("card missing the profile deep link")
-	}
-	if !strings.Contains(card, "Premium: да") {
-		t.Error("card missing the premium flag")
-	}
+func TestSupportCard(t *testing.T) {
+	t.Run("name is a plain-text mention, not a command", func(t *testing.T) {
+		u := &models.User{ID: 7, FirstName: "/start", Username: "ann", LanguageCode: "ru", IsPremium: true}
+		text, ents := supportCard(u)
+		// The name is rendered verbatim (no HTML, no escaping) at the start of the card.
+		if !strings.HasPrefix(text, "/start\n") {
+			t.Errorf("card = %q, want it to start with the raw name", text)
+		}
+		// A text_mention entity covers exactly the name with the user id — this both
+		// suppresses the "/start" command auto-detection and links the profile.
+		if len(ents) != 1 {
+			t.Fatalf("entities = %d, want 1", len(ents))
+		}
+		e := ents[0]
+		if e.Type != models.MessageEntityTypeTextMention || e.Offset != 0 || e.Length != len("/start") {
+			t.Errorf("entity = %+v, want a text_mention over the name", e)
+		}
+		if e.User == nil || e.User.ID != 7 {
+			t.Errorf("entity user = %+v, want id 7", e.User)
+		}
+		if strings.Contains(text, "tg://") || strings.Contains(text, "<") {
+			t.Errorf("card = %q, want no tg:// link and no HTML", text)
+		}
+		if !strings.Contains(text, "Premium: да") || !strings.Contains(text, "@ann") {
+			t.Errorf("card = %q, want premium + @username", text)
+		}
+	})
+
+	t.Run("entity length is UTF-16, not runes", func(t *testing.T) {
+		// "😀A" is 2 runes but 3 UTF-16 code units (the emoji is a surrogate pair).
+		u := &models.User{ID: 9, FirstName: "😀A"}
+		_, ents := supportCard(u)
+		if len(ents) != 1 || ents[0].Length != 3 {
+			t.Fatalf("entity = %+v, want length 3 UTF-16 units", ents)
+		}
+	})
+
+	t.Run("nameless user falls back to an id label", func(t *testing.T) {
+		u := &models.User{ID: 42}
+		text, ents := supportCard(u)
+		if !strings.HasPrefix(text, "user 42") {
+			t.Errorf("card = %q, want the id fallback name", text)
+		}
+		if ents[0].Length != len("user 42") {
+			t.Errorf("entity length = %d, want it over the fallback name", ents[0].Length)
+		}
+	})
 }
 
 func TestSupportTopicName(t *testing.T) {