The May 5 refactor in d5357f816 made _message_thread_id_for_typing()
symmetric with _message_thread_id_for_send() by mapping the General
topic (thread id "1") to None upfront for both. That's correct for
sendMessage — Telegram rejects message_thread_id=1 on sends and the
topic must be omitted — but it's wrong for sendChatAction.
Observed behavior (confirmed via before/after Telegram wire traces):
Before d5357f816: thread_id=1 → message_thread_id=1 → bubble visible in General
After d5357f816: thread_id=1 → message_thread_id=None → no visible typing
Omitting message_thread_id on sendChatAction does NOT fall back to
the General topic's view in a forum-enabled supergroup; the bubble
ends up hidden from the client's General-topic pane entirely. For
any user on a forum-group, the typing indicator stopped appearing.
Fix: drop the symmetric "1 → None" mapping from the typing resolver.
sendMessage still maps 1 → None via _message_thread_id_for_send (that
side was never broken). The asymmetry is real and required by
Telegram's API — document it in the resolver docstring.
Partial revert of d5357f816; restores the behavior from 0cf7d570e
("fix(telegram): restore typing indicator and thread routing for
forum General topic"). Does not re-introduce the retry-without-thread
fallback that 41545f7ec scoped down for DM topics — with the resolver
fixed, the first call already hits the right wire shape.
Test updated from test_send_typing_general_topic_uses_none_thread_id
(which encoded the broken contract) to
test_send_typing_preserves_general_topic_thread_id, asserting the
single correct call with message_thread_id=1. 10 other tests in the
file untouched and passing.