responsiveness improvements

+ extract track context menu handler into a composable

src/assets/scss/Global/app-grid.scss

@@ -1,6 +1,6 @@
 #app-grid {
   display: grid;
-  grid-template-columns: min-content 1fr min-content;
+  grid-template-columns: min-content 1fr 29rem;
   grid-template-rows: max-content 1fr max-content;
   grid-template-areas:
     "l-sidebar nav search-input"
@@ -12,6 +12,20 @@
   margin: 0 auto;
   gap: 1rem;
   margin: $small auto;
+
+  @include for-desktop-down {
+    grid-template-columns: min-content 1fr 26rem;
+  }
+
+  @include tablet-landscape {
+    grid-template-columns: min-content 1fr;
+
+    .r-sidebar,
+    #tabs,
+    #gsearch-input {
+      display: none;
+    }
+  }
 }
 
 #acontent {
@@ -30,16 +44,11 @@
   grid-area: tabs;
   height: 3.5rem;
   margin-top: -$small;
-
-  @include tablet-landscape {
-    display: none;
-  }
 }
 
 .r-sidebar {
   grid-area: r-sidebar;
   margin-top: -$small;
-  width: 29rem;
 }
 
 #gsearch-input {