Bug Fixes/Changes

• chore: fix await in cleanup script (backport: 3-0-x). #14696

• docs: specify BrowserWindow features passable to window.open. #14702

• Fix second-instance handler signature. #14748

• fix: do not set layer explicitly for frameless window. #14736

• fix: actually return appmetrics. #14750

• fix: initialize tracing controller before starting platform (3-0-x). #14503

• docs: clarify allowable background colors for BrowserWindow transparency (backport: 3-0-x). #14781

• fix: inconsistent titleBarStyle on transparent fullscreen. #14790

• chore: bump libcc (3-0-x). #14809

• fix: get background color from GtkMenuBar#menubar. #14812