cleanupExpiredRemoteClipboardFiles read the entire OS temp root with
readdir({ withFileTypes: true }) and mapped every entry into Promise.all,
so the prefix filter only ran after a promise already existed per entry.
The sweep is fire-and-forget from registerClipboardIpcHandlers at startup,
so a large %TEMP% froze the main process before the window came up.
Stream the root with opendir, skip foreign entries before allocating, and
cap in-flight removals at 8.
