Build an AI chat product UI (ChatGPT-style).
STYLE
- Dark sidebar (#0c1220), light thread area (#111827)
- 16px message bubbles, accent color for the user bubble
- Model pill inside the composer (e.g. "Sage-1")
LAYOUT
- Left conversation sidebar (~96px): "New chat" action, a list of past threads with one active, and an "Upgrade to Pro" footer
- Main thread: a greeting bubble, user and assistant messages, pinned composer at the bottom
COMPONENTS
- Conversation list with an active state
- Assistant and user message bubbles (left / right aligned)
- Composer with a placeholder, a model pill, and a round send button
TECHNICAL
- React
- Tailwind CSS
- shadcn/ui