fix: add missing files and copy data to dist for CI build

- Add src/ui/share.js (share modal, imported by app.js but not committed)
- Add public/feature-detection.js (browser capability check, static asset)
- Add src/utils/feature-detection.js (source version)
- Update build script to copy data/ directory into dist/ so domain JSON
  bundles are available at runtime on GitHub Pages

Co-Authored-By: Claude (claude-opus-4-6) <noreply@anthropic.com>

Author: jeremymanning

package.json

@@ -5,7 +5,7 @@
   "description": "Interactive Wikipedia Knowledge Map — adaptive quiz visualization using text embeddings",
   "scripts": {
     "dev": "vite",
-    "build": "vite build",
+    "build": "vite build && cp -r data dist/data",
     "preview": "vite preview",
     "test": "vitest run",
     "bench": "vitest bench",

public/feature-detection.js

@@ -0,0 +1,225 @@
+/**
+ * Feature detection for unsupported browsers (T066)
+ * Detects critical features and shows fallback message if any are missing
+ * Runs as a regular script (not type="module") to work even if ES modules fail
+ */
+
+(function() {
+  'use strict';
+
+  // Feature detection checks
+  const features = {
+    esModules: () => 'noModule' in HTMLScriptElement.prototype,
+    canvas2d: () => {
+      try {
+        const canvas = document.createElement('canvas');
+        return canvas.getContext('2d') !== null;
+      } catch (e) {
+        return false;
+      }
+    },
+    localStorage: () => {
+      try {
+        const test = '__feature_test__';
+        localStorage.setItem(test, test);
+        localStorage.removeItem(test);
+        return true;
+      } catch (e) {
+        return false;
+      }
+    },
+    cssCustomProperties: () => {
+      try {
+        const el = document.createElement('div');
+        el.style.setProperty('--test', '1px');
+        return el.style.getPropertyValue('--test') === '1px';
+      } catch (e) {
+        return false;
+      }
+    }
+  };
+
+  // Check all critical features
+  const results = {};
+  let allSupported = true;
+
+  for (const [name, check] of Object.entries(features)) {
+    try {
+      results[name] = check();
+      if (!results[name]) {
+        allSupported = false;
+      }
+    } catch (e) {
+      results[name] = false;
+      allSupported = false;
+    }
+  }
+
+  // If all features are supported, exit early
+  if (allSupported) {
+    window.__featureDetectionPassed = true;
+    return;
+  }
+
+  // Show fallback message for unsupported browsers
+  showUnsupportedBrowserFallback(results);
+
+  function showUnsupportedBrowserFallback(results) {
+    // Create fallback UI
+    const fallback = document.createElement('div');
+    fallback.id = 'unsupported-browser-fallback';
+    fallback.style.cssText = `
+      position: fixed;
+      inset: 0;
+      background: linear-gradient(135deg, #0f172a 0%, #1e293b 100%);
+      color: #f1f5f9;
+      display: flex;
+      align-items: center;
+      justify-content: center;
+      flex-direction: column;
+      padding: 2rem;
+      z-index: 99999;
+      font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
+      text-align: center;
+      overflow-y: auto;
+    `;
+
+    const content = document.createElement('div');
+    content.style.cssText = `
+      max-width: 600px;
+      background: rgba(30, 41, 59, 0.8);
+      border: 1px solid rgba(51, 65, 85, 0.6);
+      border-radius: 12px;
+      padding: 3rem 2rem;
+      backdrop-filter: blur(10px);
+    `;
+
+    const heading = document.createElement('h1');
+    heading.style.cssText = `
+      font-size: 2rem;
+      margin-bottom: 1rem;
+      font-weight: 700;
+      color: #ffa00f;
+    `;
+    heading.textContent = 'Browser Not Supported';
+
+    const message = document.createElement('p');
+    message.style.cssText = `
+      font-size: 1.1rem;
+      margin-bottom: 1.5rem;
+      line-height: 1.6;
+      color: #e2e8f0;
+    `;
+    message.textContent = 'Your browser is missing critical features needed to run the Knowledge Mapper.';
+
+    const details = document.createElement('div');
+    details.style.cssText = `
+      text-align: left;
+      background: rgba(15, 23, 42, 0.5);
+      border-radius: 8px;
+      padding: 1.5rem;
+      margin-bottom: 1.5rem;
+      font-size: 0.95rem;
+      color: #cbd5e1;
+    `;
+
+    const detailsList = document.createElement('ul');
+    detailsList.style.cssText = `
+      list-style: none;
+      padding: 0;
+      margin: 0;
+    `;
+
+    const featureNames = {
+      esModules: 'ES Module Support',
+      canvas2d: 'Canvas 2D Graphics',
+      localStorage: 'Local Storage',
+      cssCustomProperties: 'CSS Custom Properties'
+    };
+
+    for (const [feature, supported] of Object.entries(results)) {
+      const li = document.createElement('li');
+      li.style.cssText = `
+        padding: 0.5rem 0;
+        display: flex;
+        align-items: center;
+        gap: 0.75rem;
+      `;
+
+      const status = document.createElement('span');
+      status.style.cssText = `
+        display: inline-block;
+        width: 20px;
+        height: 20px;
+        border-radius: 50%;
+        background: ${supported ? '#10b981' : '#ef4444'};
+        flex-shrink: 0;
+        font-weight: bold;
+        color: white;
+        font-size: 0.8rem;
+        display: flex;
+        align-items: center;
+        justify-content: center;
+      `;
+      status.textContent = supported ? '✓' : '✕';
+
+      const label = document.createElement('span');
+      label.textContent = featureNames[feature];
+      label.style.color = supported ? '#10b981' : '#ef4444';
+
+      li.appendChild(status);
+      li.appendChild(label);
+      detailsList.appendChild(li);
+    }
+
+    details.appendChild(detailsList);
+
+    const recommendation = document.createElement('p');
+    recommendation.style.cssText = `
+      font-size: 1rem;
+      margin-bottom: 1.5rem;
+      line-height: 1.6;
+      color: #cbd5e1;
+    `;
+    recommendation.innerHTML = 'Please upgrade to a modern browser:<br><strong>Chrome 90+</strong>, <strong>Firefox 88+</strong>, <strong>Safari 15+</strong>, or <strong>Edge 90+</strong>';
+
+    const button = document.createElement('button');
+    button.style.cssText = `
+      background: linear-gradient(135deg, #00693e 0%, #1a8a5a 100%);
+      color: white;
+      border: none;
+      padding: 0.75rem 2rem;
+      border-radius: 8px;
+      font-size: 1rem;
+      font-weight: 600;
+      cursor: pointer;
+      transition: all 0.3s ease;
+      box-shadow: 0 4px 12px rgba(0, 105, 62, 0.3);
+    `;
+    button.textContent = 'Try Anyway (May Not Work)';
+    button.onmouseover = () => {
+      button.style.boxShadow = '0 6px 16px rgba(0, 105, 62, 0.5)';
+      button.style.transform = 'translateY(-2px)';
+    };
+    button.onmouseout = () => {
+      button.style.boxShadow = '0 4px 12px rgba(0, 105, 62, 0.3)';
+      button.style.transform = 'translateY(0)';
+    };
+    button.onclick = () => {
+      fallback.remove();
+      window.__featureDetectionPassed = true;
+    };
+
+    content.appendChild(heading);
+    content.appendChild(message);
+    content.appendChild(details);
+    content.appendChild(recommendation);
+    content.appendChild(button);
+
+    fallback.appendChild(content);
+    document.body.appendChild(fallback);
+
+    // Prevent app from loading
+    window.__featureDetectionPassed = false;
+  }
+})();