fix: prevent window listeners from triggering events twice (#10611)

fixes #10271
The prior fix in #10307 wasn't quite right, because JSDom has a difference between window and event.composedPath which sounds like a bug, and a workaround in that PR made it so the test did pass when the bug still occurred. That's also why there isn't a test here, because we can't properly test this using JSDom.

.changeset/fresh-impalas-bow.md

@@ -0,0 +1,5 @@
+---
+"svelte": patch
+---
+
+fix: prevent window listeners from triggering events twice

packages/svelte/src/internal/client/render.js

@@ -1401,6 +1401,7 @@ export function delegate(events) {
  * @returns {void}
  */
 function handle_event_propagation(handler_element, event) {
+	const owner_document = handler_element.ownerDocument;
 	const event_name = event.type;
 	const path = event.composedPath?.() || [];
 	let current_target = /** @type {null | Element} */ (path[0] || event.target);
@@ -1420,12 +1421,15 @@ function handle_event_propagation(handler_element, event) {
 	const handled_at = event.__root;
 	if (handled_at) {
 		const at_idx = path.indexOf(handled_at);
-		if (at_idx !== -1 && handler_element === document) {
-			// This is the fallback document listener but the event was already handled
-			// -> ignore, but set handle_at to document so that we're resetting the event
+		if (
+			at_idx !== -1 &&
+			(handler_element === document || handler_element === /** @type {any} */ (window))
+		) {
+			// This is the fallback document listener or a window listener, but the event was already handled
+			// -> ignore, but set handle_at to document/window so that we're resetting the event
 			// chain in case someone manually dispatches the same event object again.
 			// @ts-expect-error
-			event.__root = document;
+			event.__root = handler_element;
 			return;
 		}
 		// We're deliberately not skipping if the index is higher, because
@@ -1451,8 +1455,7 @@ function handle_event_propagation(handler_element, event) {
 	define_property(event, 'currentTarget', {
 		configurable: true,
 		get() {
-			// TODO: ensure correct document?
-			return current_target || document;
+			return current_target || owner_document;
 		}
 	});