applyLookAndFeel
Applies the look-and-feel named name (matched case-insensitively against installedLookAndFeels's display names, e.g. "Nimbus", "Metal", "System"), refreshing every window in windows so an already-visible IDE reflects the change immediately - not just windows created afterward. Returns whether a match was found and applied; never throws, since an invalid/unsupported name (e.g. from a stale persisted setting or a typo'd CLI flag) shouldn't crash startup or the menu action that triggered it.