fix: harden preload argv parsing for popup windows

src/preload-args.ts

@@ -0,0 +1,10 @@
+export function resolveOverlayLayerFromArgv(
+  argv: readonly string[] | null | undefined,
+): 'visible' | 'modal' | null {
+  const overlayLayerArg = argv?.find((arg) => arg.startsWith('--overlay-layer='));
+  const overlayLayerFromArg = overlayLayerArg?.slice('--overlay-layer='.length);
+
+  return overlayLayerFromArg === 'visible' || overlayLayerFromArg === 'modal'
+    ? overlayLayerFromArg
+    : null;
+}