- MobileChatView: full-screen mobile chat using 100dvh, back button, safe-area input
- ChatPanel: conditionally renders MobileChatView on mobile via useMediaQuery
- ChatConversationList: wraps ScrollArea in PullToRefresh for mobile
- ChatInput: pb-[env(safe-area-inset-bottom)] padding + 44px Send button touch target
- ChatConversationItem: min-h-[48px] touch target per UI-SPEC
- Add ChatConversationItem with DropdownMenu actions (Rename, Pin/Unpin, Archive, Delete) and active highlight
- Add ChatConversationList with IntersectionObserver infinite scroll, loading skeletons, delete confirmation dialog, and CRUD handlers
- Add ChatMessageList with auto-scroll-to-bottom on new messages and empty state
- Update ChatPanel to render ChatConversationList (left column) and ChatMessageList (right column); handleSend uses two paths: direct chatApi for new conversations, hook mutation for existing ones