A wake run whose model answered in plain final text (the coding-tuned
Kimi family does this instead of calling send_message) completed
'successfully', closed its vehicle task, and left the founder staring
at a silent conversation — the reply lived only in provider_requests.
deliverChatReplyIfMissing now runs before a chat-wake run may complete:
when the run never posted into the source thread (run-start watermark,
so a send_message it did make suppresses the fallback), its final text
is delivered as the agent's reply. A delivery failure fails the run
loudly instead of closing it on silence.