forgot to commit the portal

src/lib/components/util/Portal.svelte

@@ -0,0 +1,84 @@
+<script lang="ts">
+	import { browser } from "$app/environment";
+
+	type PortalProps = {
+		/**
+		 * Content to render into the portal target.
+		 */
+		children: import("svelte").Snippet;
+
+		/**
+		 * Optional CSS selector for the portal target element.
+		 * Defaults to `document.body`.
+		 */
+		targetSelector?: string;
+
+		/**
+		 * Optional tag name used for the created mount node.
+		 * Defaults to `div`.
+		 */
+		tagName?: keyof HTMLElementTagNameMap;
+
+		/**
+		 * Optional class applied to the created mount node.
+		 */
+		class?: string;
+
+		/**
+		 * Optional id applied to the created mount node.
+		 */
+		id?: string;
+	};
+
+	let {
+		children,
+		targetSelector,
+		tagName = "div",
+		class: className,
+		id,
+	}: PortalProps = $props();
+
+	function createMountNode() {
+		const el = document.createElement(tagName);
+		if (className) el.className = className;
+		if (id) el.id = id;
+		return el;
+	}
+
+	function resolveTarget(): Element | null {
+		if (!browser) return null;
+		if (targetSelector) return document.querySelector(targetSelector);
+		return document.body;
+	}
+
+	/**
+	 * Attachment factory: creates a mount node and appends it to the target.
+	 * MUST return either:
+	 * - void, or
+	 * - a cleanup function, or
+	 * - an object with a destroy() method
+	 *
+	 * The TS types in this project expect the cleanup-function form.
+	 */
+	function portal(node: HTMLElement) {
+		const target = resolveTarget();
+		if (!target) return;
+
+		const mount = createMountNode();
+		target.appendChild(mount);
+
+		// Move the node into the mount (portaling)
+		mount.appendChild(node);
+
+		return () => {
+			// Remove mount (also removes `node` from DOM)
+			mount.remove();
+		};
+	}
+</script>
+
+{#if browser}
+	<div {@attach portal}>
+		{@render children()}
+	</div>
+{/if}