[Fix] Auto-start channels appear unresponsive when task launch fails

[roomote-community]

Created by Roomote. Follow up by mentioning @roomote, in the web UI, or in Discord.

What changed

• Reply in Slack and Discord auto-start channels when launch classification or task startup fails unexpectedly.
• Only reply to human-authored messages: failures on bot-authored messages (e.g. automated alert or deploy feeds) stay log-only, so a sustained classifier or startup outage cannot post a retry reply for every feed message.
• Keep intentional launch-criteria skips silent (including rate-limited skips, now documented in-code) and preserve the more specific deployment read-only response.
• Make Slack routing diagnostics best-effort so diagnostic failures cannot produce false launch-failure messages or suppress real ones.

Why this change was made

Auto-start failures were previously logged without any channel response, making Roomote appear unresponsive even when it had received the message and could still communicate with the user.

Impact

Users now receive a concise retry message for recoverable auto-start failures in Slack and Discord. Successful launches, intentional criteria-based skips, and bot-authored feed messages are unchanged.

[roomote-community]

No new code issues found. See task

_{Reviewed 9cb95c0}

[daniel-lxs]

Reviewed the full diff and ran the suite locally, pushed a follow-up so failure replies are human-only, a classifier or startup outage in a channel watching a bot feed would otherwise reply to every feed message. Criteria and rate-limit skips stay silent, read-only keeps its specific message.