feat: render floating popup at extension root

src/interface/utils/portal.ts

@@ -0,0 +1,22 @@
+import type { Action } from "svelte/action";
+
+/**
+ * Svelte action that moves the element to a different DOM target.
+ * Defaults to the nearest ShadowRoot so styles remain intact when the app
+ * is rendered inside a shadow DOM. Falls back to document.body otherwise.
+ * Keeps all Svelte reactivity/events intact while escaping ancestor stacking contexts.
+ */
+export const portal: Action<HTMLElement, HTMLElement | ShadowRoot | undefined> = (node, target) => {
+  const root = node.getRootNode();
+  const dest = target ?? (root instanceof ShadowRoot ? root : document.body);
+  dest.appendChild(node);
+
+  return {
+    update(newTarget) {
+      (newTarget ?? dest).appendChild(node);
+    },
+    destroy() {
+      node.remove();
+    },
+  };
+};