setHiddenUntilMouseMoves: only hid or showed the cursor, so the flag set
by setHiddenUntilMouseMoves:YES was never cleared when the user moved the
pointer. Track and clear it in NSDisplay instead of NSCursor: add
setCursorHiddenUntilMouseMoves: and pointerMoved to the display, let the
X11 backend report genuine motion (after its synthetic warp filter), and
have NSCursor forward to the display. The idempotency guard keeps the
hide/show state balanced and preserves an explicit [NSCursor hide].