L2/SEC-004: check event.source in passkey toast closed listener

@@ -968,6 +968,9 @@968968 // inject.tsx posts this when the passkey toast closes (approve, deny, or timeout)969969 // so we know it's safe to allow autofill again.970970 window.addEventListener("message", (e: MessageEvent) => {971+  // Reject postMessages from cross-frame senders — only the same window's972+  // injected toast may flip this flag.973+  if (e.source !== window) return;971974   const d = e.data as { source?: string; type?: string } | undefined;972975   if (d?.source === "peach-passkey-toast" && d?.type === "toast-closed") {973976     passkeyToastActive = false;