[ghost]

Summary

Hosts that mirror a user's input from another surface (for example Moyai's web UI) can now post it in Slack under that user's name and avatar, the way Devin does, instead of under a bot header.

• message_request(..., username=None, icon_url=None) passes through to MessageRequest::new(..., author: Option<&SlackAuthor>, ...). Both fields go only on chat.postMessage; chat.update ignores them. The username is whitespace-collapsed and must be 1-80 chars. icon_url must be https:// with no userinfo and at most 2048 chars. An icon_url without a username is rejected.
• Slack only honors these fields when the bot has chat:write.customize (see docs/slack.md).
• thread_context previously attributed our own bot's history messages by sender id. It now uses the custom username they were posted with, so the model sees "Ishaan Jaffer: continue" and not a bot message.

Link to Devin session: https://app.devin.ai/sessions/86a7a2fbcc4b422ea615fa8f7c82f1a8
Open in Devin Desktop: https://app.devin.ai/desktop/session/86a7a2fbcc4b422ea615fa8f7c82f1a8?variant=devin
Requested by: @ishaan-berri

[devin-ai-integration]

I'll fix CI failures and address comments from users with write access. I'll skip comments containing "(aside)".

• Disable automatic comment, CI, and merge conflict monitoring