Five small fixes against issues filed during the post-merge salvage audit:
* #28670: `_GATEWAY_PROVIDER_ERROR_RE` false-positives on legitimate prose.
Replace the regex with an anchored `_GATEWAY_PROVIDER_ERROR_SHAPE_RE` and
add a length-cap heuristic to `_looks_like_gateway_provider_error`:
short envelope at the start of the message → real provider error; long
prose containing 'HTTP 404' → assistant answer, leave alone.
* #28672: drop the pointless 1s asyncio.sleep on Telegram thread-not-found
retries. The same-thread retry is preserved (catches Telegram's
occasional transient flake exercised by
test_send_retries_transient_thread_not_found_before_fallback) but with
no artificial delay.
* #28674: broaden `_should_retry_without_dm_topic_reply_anchor` to also
fire when Bot API rejects `direct_messages_topic_id` for synthetic /
resumed sends that have no reply anchor. Avoids dropping post-resume
background notifications if the topic id goes stale.
* #28676: delete the dead image-document branch superseded by bd0c54d17
(which returns early on the same extension set).
* #28678: extend chat-scoped allowlist (`TELEGRAM_GROUP_ALLOWED_CHATS`)
to also cover `chat_type == 'channel'`, so operators can authorize
channel posts by chat id without falling back to per-user allowlists.
Tests:
- scripts/run_tests.sh tests/gateway/test_telegram_thread_fallback.py -q → 41/41
- scripts/run_tests.sh tests/cron/test_scheduler.py -q → 127/127
- broader test set: same 3 pre-existing test-pollution failures reproduce
on plain main.
a3c753128d