fixed site docs behavior on narrow screens

site/src/jsTest/kotlin/AppResponsiveTocTest.kt

@@ -0,0 +1,33 @@
+/*
+ * Copyright 2026 Sergey S. Chernov real.sergeych@gmail.com
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+import kotlin.test.Test
+import kotlin.test.assertFalse
+import kotlin.test.assertTrue
+
+class AppResponsiveTocTest {
+    @Test
+    fun tocIsCollapsedBelowLgBreakpoint() {
+        assertFalse(isDesktopTocLayout(991))
+    }
+
+    @Test
+    fun tocStaysDesktopAtLgBreakpointAndAbove() {
+        assertTrue(isDesktopTocLayout(992))
+        assertTrue(isDesktopTocLayout(1280))
+    }
+}