Cherry-picked from PR #10371. Two-layer defense for the spurious-thread_id
issue (#3206):
1. _build_message_event filters DM thread_ids: only preserve thread_id
for real topic messages (is_topic_message=True). Telegram puts
message_thread_id on every DM that is a reply, but reply-chain ids
route to nonexistent threads on send.
2. _send_message_with_thread_fallback helper: control sends
(send_update_prompt, send_exec_approval / send_slash_confirm,
send_model_picker) retry once without message_thread_id when
Telegram returns BadRequest 'Message thread not found'. Mirrors
the pattern PR #3390 added for the streaming send path.
Salvage notes:
- Conflict 1 (line ~4099): merged the contributor's DM is_topic_message
filter with the existing forum General-topic default from #22423,
preserving both behaviors.
- Conflict 2 (line ~1664 / 1690): kept main's delete_message (PR #23416)
alongside the new helper. Tightened the helper's exception catch
from bare 'Exception' to use the existing _is_bad_request_error +
_is_thread_not_found_error helpers (line 484-496) for consistency
with the streaming send path.
- Widened the fix to send_update_prompt (was bare self._bot.send_message,
same bug class).
Authored by rahimsais via PR #10371 (re-attributed from donrhmexe@
local commit author).
