Why: The design system still described preview as a right-rail tab, while the implementation now keeps a timeline in the transcript and opens files in a closable pane beside the chat. Evidence: make test passed (core, backend, frontend 51, ui 71, agent-command). Impact: Dev pins core d437530, backend dab8f31, ui 8bfe8a8, frontend 0ed8ad3. DESIGN.md §6, §9.3, and §9.6 match that layout. Refs: feature/chat-timeline-preview Co-authored-by: Cursor <cursoragent@cursor.com>
ui
@ 8bfe8a89db