fix(gateway): honor server retry_after in _send_with_retry for Telegram flood control (#46762)

When Telegram's sendRichMessage returns a FloodWait/RetryAfter error,
_try_send_rich() now extracts the server-provided retry_after value and
propagates it through SendResult.retry_after. The base _send_with_retry()
layer honors this value instead of using its default short exponential
backoff (~2s, ~4s), preventing the retry budget from being exhausted
against a server that demands a 25-37s wait.

Salvaged from #46774 by @liuhao1024. Telegram adapter path moved from
gateway/platforms/telegram.py to plugins/platforms/telegram/adapter.py
since the original PR.

Closes #46762

plugins/platforms/telegram/adapter.py

@@ -1378,6 +1378,15 @@ class TelegramAdapter(BasePlatformAdapter):
                 _TimedOut = None
             is_timeout = (_TimedOut and isinstance(exc, _TimedOut)) or "timed out" in err_str
             is_connect_timeout = self._looks_like_connect_timeout(exc)
+            # Extract server-requested retry_after for flood control so the
+            # base retry layer honors Telegram's backoff instead of its own
+            # short exponential schedule.
+            _retry_after = getattr(exc, "retry_after", None)
+            if _retry_after is None:
+                import re as _re
+                _m = _re.search(r"retry\s+(?:in\s+)?(\d+)", err_str, _re.IGNORECASE)
+                if _m:
+                    _retry_after = float(_m.group(1))
             logger.warning(
                 "[%s] sendRichMessage transient failure (no legacy resend): %s",
                 self.name, exc,
@@ -1386,6 +1395,7 @@ class TelegramAdapter(BasePlatformAdapter):
                 success=False,
                 error=str(exc),
                 retryable=(is_connect_timeout or not is_timeout),
+                retry_after=_retry_after,
             )
 
         message_id = None