On a MacBook the window had last been zoomed. magpie skipped a maximised
window when it saved the size, so it reopened at an older, nearly full
size: 1712×1083 at (8,34) on a 1728×1084 work area, neither full nor the
size it was given nor the default.
settings.WindowMaximised (this computer's own, KeepOwn) now records
whether the window was maximised when it settled; Window stays the size
it restores to (settle). A window not shown yet, let go, full screen or
minimised, or on Linux hidden, records nothing.
Reopened maximised: on the Mac and Windows placeMain maximises the made
window just before its first Show (on Windows once its page has come);
Wails' StartState is undone by the Mac's centring and shows a Windows
window before its page. The least size Maximise drops is put back. On
Linux makeMain sets StartState, since GTK can't be asked about a window
not mapped yet.
A size kept on a larger screen: Windows fits the window to the work area
and centres it, title bar in reach, and keeps the larger size for the
larger screen (fitted); the Mac fits and zooms it itself, and magpie
doesn't zoom it again, so it can still be restored.
TestSettle fails with upstream's rule (5 of 9 cases); TestOpenSize,
TestFitRoom, TestWindowMaximisedKeptAndOwn; the Mac's real build under a
sandbox HOME, 11 cases.