[FEATURE] Richer TUI — sidebar with context/token usage, cleaner message layout

Summary

The current Claude Code terminal UI is functional but minimal. Tools like OpenCode demonstrate what a richer TUI can look like — and many Claude Code users are considering switching purely for the interface, even though that means paying extra API costs on top of a Pro subscription.

What OpenCode does that Claude Code doesn't

• Sidebar panel showing: session timestamp, token count, % context used, cost spent, LSP status
• Clean message bubbles with clear visual separation between user and assistant turns
• Distinct color coding for errors, tool output, and responses
• Static layout — the UI doesn't reflow/flicker as responses stream in

Request

Adopt similar layout improvements natively in Claude Code's TUI so Pro/Max subscribers get a polished experience without needing a separate tool that requires additional API credits.

Specific asks:

1. Live token count and context % used visible during the session
2. Cost tracking display ($ spent this session)
3. Cleaner visual separation between user/assistant messages
4. Stable, non-flickering layout during streaming responses
5. Auto-scroll control — ability to scroll up and read earlier parts of a long response without being pulled back to the bottom; pause-on-scroll-up with a manual resume (e.g. Ctrl+End)

Why it matters

Claude Code is the only tool that works with Claude Pro/Max subscriptions. Users who want a better interface are forced to either accept the current minimal UI or pay extra for API access on top of their subscription. Closing this gap would reduce churn and improve daily usability for power users.