Emdash source with visual editor image upload fix

Fixes:
1. media.ts: wrap placeholder generation in try-catch
2. toolbar.ts: check r.ok, display error message in popover

packages/admin/tests/setup.ts

@@ -0,0 +1,5 @@
+import "vitest-browser-react";
+import { i18n } from "@lingui/core";
+
+// Initialize i18n for browser tests with empty English messages
+i18n.loadAndActivate({ locale: "en", messages: {} });