feat: 場景8加入三個連結按鈕

- 📚 教學：查看教學指南
- 💻 GitHub：查看 repository 和 issues/PR
- 🎯 Demo：查看待辦事項應用

新增 btn-repo 樣式和 scenario-links-3 布局支援三個按鈕

Author: yulin0629

index.html

@@ -174,6 +174,31 @@
             box-shadow: 0 3px 10px rgba(0,0,0,0.2);
         }
 
+        .btn-repo {
+            background: rgba(128, 90, 213, 0.9);
+            color: white;
+            font-weight: 600;
+        }
+        
+        .btn-repo:hover {
+            background: rgba(107, 70, 193, 0.9);
+            box-shadow: 0 3px 10px rgba(0,0,0,0.2);
+        }
+        
+        /* 三個按鈕的特殊布局 */
+        .scenario-links-3 {
+            flex-wrap: wrap;
+            justify-content: center;
+        }
+        
+        .scenario-links-3 .btn {
+            font-size: 0.85rem;
+            padding: 6px 12px;
+            flex: 1;
+            min-width: 70px;
+            text-align: center;
+        }
+        
         .btn-primary {
             background: #667eea !important;
             color: white !important;
@@ -514,9 +539,10 @@ <h2>📚 8 個學習場景</h2>
                         <div class="scenario-title">GitHub 自動化 Agent</div>
                         <div class="scenario-description">從 Issue 到 PR 的完整自動化流程</div>
                         <span class="agent-indicator agent-90">Agent 90%</span>
-                        <div class="scenario-links">
-                            <a href="#" onclick="loadMarkdown('./08-comprehensive-project/TEACHING_GUIDE.md', '場景 8：GitHub 自動化 Agent'); return false;" class="btn btn-doc">📚 查看教學</a>
-                            <a href="https://yulin0629.github.io/copilot-agent-demo-todo/" target="_blank" class="btn btn-demo">🎯 實際應用</a>
+                        <div class="scenario-links scenario-links-3">
+                            <a href="#" onclick="loadMarkdown('./08-comprehensive-project/TEACHING_GUIDE.md', '場景 8：GitHub 自動化 Agent'); return false;" class="btn btn-doc">📚 教學</a>
+                            <a href="https://github.com/yulin0629/copilot-agent-demo-todo" target="_blank" class="btn btn-repo">💻 GitHub</a>
+                            <a href="https://yulin0629.github.io/copilot-agent-demo-todo/" target="_blank" class="btn btn-demo">🎯 Demo</a>
                         </div>
                     </div>
                 </div>