Improve Media Manager transition after matching wizard

- Removed full-page 'Connecting...' loading screen after matching modal closes.
- Ensured main UI (SKU info and gallery shell) appears immediately after the wizard.
- Leveraged grid-level loading indicator for non-blocking background refresh.
- Verified transition stability with integration and handler tests.

src/MediaManager.html

@@ -1953,7 +1953,7 @@
 
       startMatching() {
         document.getElementById('loading-ui').style.display = 'none';
-        document.getElementById('main-ui').style.display = 'none';
+        document.getElementById('main-ui').style.display = 'block';
         document.getElementById('matching-modal').style.display = 'flex';
         this.renderMatch();
       },
@@ -2071,8 +2071,12 @@
 
         // All Done
         document.getElementById('matching-modal').style.display = 'none';
-        ui.logStatus('info', 'Matching complete. Reloading...', 'info');
-        document.getElementById('loading-ui').style.display = 'block';
+        ui.logStatus('info', 'Matching complete. Finalizing gallery...', 'info');
+
+        // Show main UI immediately if not already showing
+        document.getElementById('main-ui').style.display = 'block';
+        document.getElementById('loading-ui').style.display = 'none';
+
         // Reload to get fresh state. Since hasRunMatching is true, it shouldn't trigger again.
         this.loadMedia(true);
       },