[ishaan-berri]

Summary

The Slack socket transport adds 👀 (ack_emoji="eyes") before it dispatches a message. Durable hosts that only use SlackHost (e.g. Moyai's signed HTTP inbox) never got that, so each host had to hand-roll reactions.add. This PR moves the ack into SlackHost, using the same request(api_method, payload) callback convention as upload_slack_files:

host = SlackHost(bot_user_id=..., workspace_id=..., ack_emoji="eyes")  # default "eyes"; None disables
event = host.normalize_event(payload)
# after the host decides to handle it, before slow work:
ok: bool = await host.acknowledge(event, request, timeout=3.0)
# -> request("reactions.add", {"channel": channel_id, "name": "eyes", "timestamp": message_ts})

Semantics:

• Best effort, like the transport's _ack. It returns True on ok or on already_reacted (replays).
• It returns False when disabled, on a Slack error, on timeout, or when the callback raises any Exception.
• CancelledError propagates.
• An invalid origin or timeout raises ValueError before the callback runs.

Core: host::ack_request, host::ack_accepted and SlackHost::acknowledgement are now the single payload source. socket.rs and the Python transport _ack both use them, with no behavior change.

Consumer: BerriAI/moyai#547

Link to Devin session: https://app.devin.ai/sessions/3d913080cfd147d1a3a4fd6db2988d5b
Open in Devin Desktop: https://app.devin.ai/desktop/session/3d913080cfd147d1a3a4fd6db2988d5b?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