Add an onboarding empty state for brand-new sessions #32
Description
Summary
Right now, a new session relies heavily on the user already understanding models, permissions, and available tools. A stronger empty state could explain how to get from install to first successful response.
Acceptance Criteria
- Add a visible first-session empty state with setup and usage guidance.
- Surface the active provider and whether it appears ready.
- Link or point to Settings from the empty state.
- Avoid adding clutter once the user has already started chatting.