feat(showcase): add click-to-expand modal for screenshot

src/pages/index.astro

@@ -55,14 +55,46 @@ const version = pkg.version ?? "";
               <p>Native desktop app powered by Tauri v2. Clean, fast, and built for real development workflows. AI chat integrated seamlessly alongside your code.</p>
               <div class="feature-tag">LIVE PREVIEW</div>
             </div>
-            <div class="showcase-image-box">
+            <div class="showcase-image-box" onclick="openModal()">
               <img width="800" src="/screenshot-1.png" alt="Zaguán Blade editor interface" />
+              <div class="showcase-overlay">
+                <span>Click to expand</span>
+              </div>
             </div>
           </div>
         </div>
       </div>
     </section>
 
+    <!-- Screenshot Modal -->
+    <div id="screenshot-modal" class="modal" onclick="closeModal(event)">
+      <div class="modal-content" onclick="event.stopPropagation()">
+        <span class="modal-close" onclick="closeModal()">&times;</span>
+        <img width="1200" src="/screenshot-1.png" alt="Zaguán Blade editor interface full size" />
+      </div>
+    </div>
+
+    <script is:inline>
+      function openModal() {
+        const modal = document.getElementById('screenshot-modal');
+        modal.classList.add('active');
+        document.body.style.overflow = 'hidden';
+      }
+      
+      function closeModal(event) {
+        if (event && event.target !== event.currentTarget) return;
+        const modal = document.getElementById('screenshot-modal');
+        modal.classList.remove('active');
+        document.body.style.overflow = '';
+      }
+      
+      document.addEventListener('keydown', function(e) {
+        if (e.key === 'Escape') {
+          closeModal();
+        }
+      });
+    </script>
+
     <!-- Features Section -->
     <section id="features" class="features">
       <div class="features-header">