refactor(dashboard): extract modular Preact component structure

Replace the monolithic single-file dashboards (dashboard.html,
dashboard-preact.html) with a proper modular directory structure:

  dashboard/
    index.html              - Entry point, loads main.js
    main.js                 - App bootstrap, mounts <App> to #root
    styles.css              - Global styles (dark theme, typography)
    components/
      App.js                - Root component, state management, polling
      Header.js             - Top bar with refresh/timing info
      Sidebar.js            - Project tree navigation
      SessionCard.js        - Individual session card with status/actions
      SessionGroup.js       - Group sessions by project path
      Modal.js              - Full conversation viewer overlay
      ChatMessages.js       - Message list with role styling
      MessageBubble.js      - Individual message with markdown
      QuestionBlock.js      - User question input with quick options
      EmptyState.js         - "No sessions" placeholder
      OptionButton.js       - Quick response button component
      SimpleInput.js        - Text input with send button
    lib/
      preact.js             - Preact + htm ESM bundle (CDN shim)
      markdown.js           - Lightweight markdown-to-HTML renderer
    utils/
      api.js                - fetch wrappers for /api/* endpoints
      formatting.js         - Time formatting, truncation helpers
      status.js             - Session status logic, action availability

This structure enables:
- Browser-native ES modules (no build step required)
- Component reuse and isolation
- Easier styling and theming
- IDE support for component navigation

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

dashboard/utils/api.js

@@ -0,0 +1,20 @@
+// API Constants
+export const API_STATE = '/api/state';
+export const API_STREAM = '/api/stream';
+export const API_DISMISS = '/api/dismiss/';
+export const API_RESPOND = '/api/respond/';
+export const API_CONVERSATION = '/api/conversation/';
+export const POLL_MS = 3000;
+export const API_TIMEOUT_MS = 10000;
+
+// Fetch with timeout to prevent hanging requests
+export async function fetchWithTimeout(url, options = {}, timeoutMs = API_TIMEOUT_MS) {
+  const controller = new AbortController();
+  const timeoutId = setTimeout(() => controller.abort(), timeoutMs);
+  try {
+    const response = await fetch(url, { ...options, signal: controller.signal });
+    return response;
+  } finally {
+    clearTimeout(timeoutId);
+  }
+}