Replace recursive Card-in-Card with flat thread layout:
- One Card per comment thread, parent + all replies flat inside
- Replies separated by border-t, not nested Cards
- CommentRow component handles each individual comment (header + content + edit)
- Three-dot menu shows active state when open (data-[popup-open])
- ReplyInput simplified: avatar + editor + submit button, no extra border container
- Nested replies collected recursively but rendered flat
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
0c8738676c