fix(meshcore): show mode panel when active

meshcore.css was missing the .active display rule, so the meshcoreMode
div (display:none inline) was never made visible when the mode was
selected, leaving only the generic sidebar visible.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

static/css/modes/meshcore.css

@@ -1,12 +1,16 @@
 /* Meshcore mode — scoped styles */
 
 #meshcoreMode {
-    display: flex;
-    flex-direction: column;
+    display: none;
+    flex-direction: row;
     height: 100%;
     gap: 0;
 }
 
+#meshcoreMode.active {
+    display: flex !important;
+}
+
 /* ── Sidebar ── */
 .meshcore-sidebar {
     width: 220px;