fix(ui): portal menus to body above the sidedocks

src/ui/app.svelte

@@ -18,14 +18,23 @@
 
   let { app, store, settings, component }: Props = $props();
 
-  let root = $state<HTMLElement | null>(null);
+  // Menus hang off body, not off the view: Obsidian's sidedocks paint above the
+  // leaf, so anything portalled inside it is covered once it crosses a pane edge.
+  // The layer carries .bcal-root so the theme aliases still reach the popovers.
+  const layer = document.createElement("div");
+  layer.className = "bcal-root bcal-portal";
+
+  $effect(() => {
+    document.body.append(layer);
+    return () => layer.remove();
+  });
 
   provideView({
     app,
     store,
     settings,
     component,
-    portal: () => root as HTMLElement,
+    portal: () => layer,
   });
 
   let creating = $state(false);
@@ -56,7 +65,7 @@
   }
 </script>
 
-<div bind:this={root} class="bcal-root">
+<div class="bcal-root">
   <div class="bcal-app">
     {#if !store.railCollapsed}
       <SphereRail />