Add foldable split-pane layout

web/src/index.css

@@ -131,6 +131,45 @@ textarea {
   }
 }
 
+@media (horizontal-viewport-segments: 2) {
+  .app-safe-frame {
+    padding:
+      max(0.5rem, var(--safe-area-top))
+      max(0.5rem, var(--safe-area-right))
+      max(0.5rem, var(--safe-area-bottom))
+      max(0.5rem, var(--safe-area-left));
+  }
+
+  .workspace-shell {
+    display: grid;
+    grid-template-columns:
+      calc(env(viewport-segment-width 0 0) - max(0.5rem, var(--safe-area-left)))
+      calc(env(viewport-segment-width 1 0) - max(0.5rem, var(--safe-area-right)));
+    column-gap: calc(env(viewport-segment-left 1 0) - env(viewport-segment-right 0 0));
+  }
+
+  .workspace-sidebar {
+    position: static;
+    width: 100%;
+    max-width: none;
+    transform: none;
+    border-width: 1px;
+    border-radius: 1rem;
+  }
+
+  .workspace-content {
+    min-width: 0;
+    border-width: 1px;
+    border-radius: 1rem;
+    touch-action: auto;
+  }
+
+  .workspace-sidebar-backdrop,
+  .workspace-sidebar-trigger {
+    display: none;
+  }
+}
+
 .glass-panel {
   background:
     linear-gradient(180deg, hsl(243 42% 12% / 0.88), hsl(236 48% 5% / 0.92)),