fix(dashboard): chat mobile single-pane, comment-box theme, ChatView FOUC

- ChatView mobile: add @media (max-width: 768px) so the session-list
  sidebar goes full-width and the thread is hidden when the sidebar
  is visible (and vice-versa). The component already had the state,
  back-button (ChevronLeft), and visibility toggling — only the CSS
  was missing.
- TaskComments compose/edit textareas now use var(--surface) for
  background. The base .spec-editor-feedback uses var(--bg), which
  in light theme resolves to #ffffff — the same as the task detail
  modal's --card panel — making the comment box invisible.
- ChatView CSS is now imported eagerly from App.tsx so it bundles
  into the main CSS file. Previously the lazy ChatView JS chunk
  loaded its CSS via an async <link> tag, producing a brief flash
  of unstyled chat UI on first render.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/getting-started.md

@@ -130,7 +130,7 @@ fn dashboard
 
 On first launch, Fusion automatically opens the **onboarding wizard**. It guides you through three steps:
 
-1. **AI Setup** — Connect an AI provider and choose a default model. Authenticate via OAuth login (for supported providers like OpenAI Codex) or enter an API key directly.
+1. **AI Setup** — Start with a simplified quick-start list of recommended providers (`anthropic`, `openai`, `google`, `gemini`, `ollama`), plus any providers you already connected. You only need one provider to get started. Additional providers and detailed setup guidance live under the **Advanced provider settings** disclosure. Authenticate via OAuth login (for supported providers like OpenAI Codex) or enter an API key directly.
 
 2. **GitHub (Optional)** — Connect GitHub to import issues and manage pull requests. This step is optional — you can continue without GitHub.