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>
Why: The approved frontend redesign requires a durable design constitution
so future UI work stays consistent (user directive: make this project's
standing design guidance, four principles: beautiful/modern/concise/usable).
DESIGN.md encodes the Zai-calibrated rules (surface ladder, type scale,
radius nesting, MotionKit recipes, ToolBlock contract, IA principles) and
AGENTS.md adds a mandatory UI gate; submodules land phase 1 (tokens v3,
MotionKit, Collapsible, panel layout, mono primary buttons).
Evidence: make test in this worktree -> frontend 38 passed (incl. new
host design-guard ratchet), ui 61 passed (incl. collapsible + design-guard),
go core/backend/agent-command ok. precheck READY at R0 0be23f9a4d.
Impact: gitlinks advance to Agent-System-UI/Agent-System-Frontend
feature/ui-tokens-v3 heads; AGENTS.md gains a UI section; no backend or
contract changes.
Refs: session-approved redesign plan v2 (8 decisions recorded in task card).
weichenandCursor