Touchpad fixes from user testing: - SpinBox: the wheel only steps a FOCUSED field — hover-wheel is inert, so two-finger scrolling across a dialog no longer drifts values. - SpinBox: direct numeric entry — double-click opens the editor (the app's text input; commit on blur, Escape cancels), typing a digit on the focused field starts editing with that character. Previously the field accepted no text at all. - ComboBox: a click anywhere outside closes the open popup (on_mouse_down_out). - gpui bump: the timeline header-occlusion fix.