Bot Ingest Route

Channel-memory ingestion. Stores messages ONLY for channels connected to a workspace (same channel-scoping rule as /answer): an unconnected channel stores nothing and returns connected=false so the bot can stop sending for a while.

Also the reply-trigger signal: bot_thread=true means at least one ingested human message replies/threads onto a bot-authored message, so the bot process should follow up via /answer (whose own rate limit throttles replies).