UI: Limit the width of dialog screens, and keep content off the edges of large screens

Dialog screens (tabbed, two-pane, simple and the others built on
UIBaseDialogScreen) center their content at up to 1400 wide, instead of
stretching settings rows and buttons across very wide windows.

On large screens, those screens and the main screen also get an inset on all
sides, since controls right at the edge are hard to see there. It grows with
the screen's smaller dimension, from nothing at 600 to the full inset at
1000, and is always full on TVs. The game, popups, and the screens that
position things to match the game's screen (display layout, touch control
layout and tests, custom button and visual mapping) are left as they were.

The root's bounds are computed by UIScreen::GetContentBounds, since
UI::Margins can't hold widths this large.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

UI/TouchControlLayoutScreen.h

@@ -26,6 +26,8 @@ class ControlLayoutView;
 
 class TouchControlLayoutScreen : public UIBaseDialogScreen {
 public:
+	// The controls go where they will be in the game.
+	bool LimitContentArea() const override { return false; }
 	TouchControlLayoutScreen(const Path &gamePath) : UIBaseDialogScreen(gamePath) {}
 
 	void CreateViews() override;