set_tokens/set_iterations were never called and the two rows permanently
showed "-", so they were dead noise in the right column. Remove the rows
and their setters.

Co-Authored-By: Claude <noreply@anthropic.com>

- Add TuiSettings persisted in ~/.navi_code/tui.json (theme, mouse, scroll_speed, diff_style, keybinds).
- TUI applies saved theme/mouse on startup; CLI gets --theme override.
- Add /themes picker with live preview and /mouse toggle command.
- Extend StatusPanel with backend URL, current theme, tokens/iter placeholders.
- Fix TuiContext.app() to use Textual active_app ContextVar.
- Add unit tests for settings, themes, and status panel.

513 passed, 1 skipped. Ruff clean.

Signed-off-by: Eugene Sukhodolskiy <eugene.sukhodolskiy@gmail.com>

- Register Navi themes as Textual themes so $tui-* CSS variables resolve.

- Update ChatPanel, StatusPanel, InputBox to use palette colors.

- Update all content renderers to draw from the active theme.

- Add set_active_theme/get_active_theme helpers for runtime color access.

Co-Authored-By: Claude <noreply@anthropic.com>

- Add clients/terminal/tui package with micro-architecture:
  - events, context, chat_model, ws_bridge, permissions engine.
  - widgets: ChatPanel, StatusPanel, InputBox.
  - renderers: user/assistant messages, thinking, tool calls, errors,
    markdown, plain — registry-based and extensible.
  - slash commands: /help, /new, /sessions, /switch, /profile, /thinking,
    /compact, /quit — registry-based and extensible.
- Wire navi-code to launch TUI by default; keep click-CLI via --raw.
- Add textual>=0.70 dependency.
- Add TUI smoke tests via Textual Pilot.
- Add docs/plan_navi_code_tui.md with full Phase 4/5 roadmap.

Tests: 463 passed, 1 skipped (excluded unrelated websocket test).

Co-Authored-By: Claude <noreply@anthropic.com>