Replace the chat-printed session list with a modal picker:
- SessionsPickerScreen lists only navi_code-profile sessions (filtered by
  settings.default_profile_id), with a filter input, a top "✚ New session"
  row, and the current session marked. Up/Down + Enter to pick, Esc cancels.
- /sessions pushes the screen. Selecting an existing session runs
  _switch_session_worker (persist via StateManager + attach_session, which
  replays history and restarts the WS bridge — no chat_panel.clear() after,
  since load_history already replaces the chat and clearing would erase the
  replayed history). The "New session" row runs _create_new_session_worker.

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

Drop the SessionsPanel widget and all dead code wired to it (handlers,
broadcast helper, session-list events, _refresh_sessions worker). The
/new, /sessions, /switch commands are preserved — they already operate
via app.attach_session / chat output rather than the panel.

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

- Fix raw CLI session API fields (session_id/name/preview)

- Add --mouse/--no-mouse flags and persistent TUI settings coercion

- Make attach_session/apply_theme public, add ChatPanel.clear()

- Deduplicate session selection handlers and editor error handling

- Update docs and tests

- Add right-side SessionsPanel widget (DataTable) listing server sessions.
- Wire SessionsPanel into TUI layout and session selection flow.
- Add SessionSelected / SessionListUpdated events and refresh logic.
- Implement /export slash command: markdown rendering + $EDITOR.
- Update /new, /sessions, /switch, /profile to use session_id/name/preview.
- Add integration tests for SessionsPanel and /export; update layout test.
- Update docs/navi_code_cli.md with new panel and command.

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>

- 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>