feat: partition main canvas vertically (#6759)

Co-authored-by: Marcel Mraz <marcel.mraz@adacta-fintech.com>
Co-authored-by: dwelle <luzar.david@gmail.com>

src/css/styles.scss

@@ -3,8 +3,9 @@
 
 :root {
   --zIndex-canvas: 1;
-  --zIndex-wysiwyg: 2;
-  --zIndex-layerUI: 3;
+  --zIndex-interactiveCanvas: 2;
+  --zIndex-wysiwyg: 3;
+  --zIndex-layerUI: 4;
 
   --zIndex-modal: 1000;
   --zIndex-popup: 1001;
@@ -69,10 +70,19 @@
 
     z-index: var(--zIndex-canvas);
 
+    &.interactive {
+      z-index: var(--zIndex-interactiveCanvas);
+    }
+
     // Remove the main canvas from document flow to avoid resizeObserver
     // feedback loop (see https://github.com/excalidraw/excalidraw/pull/3379)
   }
 
+  &__canvas-wrapper,
+  &__canvas.static {
+    pointer-events: none;
+  }
+
   &__canvas {
     position: absolute;
   }