httpx timeout exceptions (ConnectTimeout, ReadTimeout, ...) stringify to
"" so every adapter log line built from _redact_telegram_error_text()
ended with a blank reason. Fall back to the exception class name.
Partial salvage of #111222: only the _redact_telegram_error_text hunk;
the transport-layer and polling-recovery hunks are covered by #111221.
ff307aea5e