Replies (messages with parentInteractionId) now open in a right-hand ThreadPane
instead of inline quoting:
- extracted a shared Composer (draft + @mention autocomplete + attach) and
MessageItem (bubble + mentions + attachment + reactions + reply affordance)
- Thread shows top-level messages only; a message with replies gets a
'💬 N replies' link, and hovering shows 💬 'Reply in thread'
- ThreadPane renders the root + its replies + a composer that posts back with
parentInteractionId; Messenger becomes 3-column (list | thread | pane),
pane closes on conversation switch
- no contract/adapter/backend change (parentInteractionId was already wired)
- thread-pane render test (open → reply → parent shows the count); 58 green
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
