Long assistant messages vanished past the chat panel's right edge instead
of wrapping: ThemedMarkdownRenderable built its rich Console at
console.width, which is the physical terminal width (e.g. 80), but the
markdown lives in a narrower Panel. options.max_width holds the real
available columns (panel inner width minus borders/padding); rich wrapped
to the terminal width while the visible area was narrower, so the right
side of every long line was cut off. Use options.max_width, falling back to
console.width only when it is unset.

- Add CommandPaletteScreen modal with fuzzy filtering and keyboard navigation.

- Bind Ctrl+P to push the palette; selected commands execute via registry.

- Make MarkdownRenderer theme-aware: headings, inline code, links, and code blocks use gnexus palette.

- Pick dracula/github-light code theme based on active theme brightness.

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>