The manifest was missing scopes required for conversations.open API,
which is used to get DM channel IDs for replies.
Added scopes:
- im:write (required for DM replies)
- im:read (list DM conversations)
- mpim:write (reply to multi-person DMs)
- mpim:read (list MPDMs)
- groups:write (private channel interactions)
- groups:read (list private channels)
Without im:write, the example config (dm.enabled: true) cannot
actually reply to DMs - fails with missing_scope error.
