host the modals in the window instead of in windows of their own

Every dialog was an OS window with a dim widget behind it in the game
window. That is why a click beside one could not reach it: Qt drops mouse
events for a window a modal blocks, so the dim -- a child of the blocked
window -- never saw the press.

ModalLayer is that dim grown up: still a child of the main window covering
its rect, but it now hosts the open modal, places it, and runs its event
loop, so it is the widget the clicks beside a modal land on. It keeps a
stack, paints one dim however many modals are open, and a hold keeps it up
while one modal hands over to the next. ModalDimOverlay and ModalDimScope
are gone; ModalLayerHold replaces the scope at the sites that still open a
system message box.

ModalDialog is what a dialog inherits in place of the window it lost: the
panel background, the drawn header with its optional close button, and the
dismissal gestures. isDismissible() governs Q and, next, the click outside
-- one predicate because both gestures reach the same dialogs. Its default
refuses, so a dialog opts in. requestDismiss() is what a gesture asks for,
and ShipLayoutDialog overrides it with the one-step ladder its Q handler
used to spell out, which is now reached by both. DialogDismiss.h folded into
the base.

The four dialogs the player meets keep their contents unchanged and lose
their title bars: the recipe/schematic selection, blueprint selection, ship
layout, and schematic choice dialogs. Placement moved with them --
placeOnSelectionPanel became getSelectionPanelAnchor, and the layer centers
on that rectangle in window coordinates, with no global mapping and no
frame height to guess at.

Two things followed from dropping OS modality: the focus guard that hands
focus back to the game world now also asks the layer whether a modal is
open, and closeEvent refuses to close the window while one is, since its
nested loop runs over widgets the window owns.

The escape menu, the game-over and win screens, and the two name dialogs are
still system dialogs; they are dimmed by a layer hold until they are
converted next.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Ne3mejABZoLWKLh8fgpM3x

src/ui/SchematicChoiceDialog.h

@@ -2,18 +2,19 @@
 
 #include <vector>
 
-#include <QDialog>
-
+#include "ModalDialog.h"
 #include "SchematicChoiceOption.h"
 
 struct RecipesConfig;
 class BuildingIconCache;
 class ItemIconCache;
 
-// The drop's choice dialog (REQ-DEF-SCHEMATIC-DROP). Unlike every other dialog it
-// cannot be dismissed: clicking an option is the only way out, so getChosenIndex()
-// always names an option the player picked, and exec() only ever returns Accepted.
-class SchematicChoiceDialog : public QDialog
+// The drop's choice dialog (REQ-DEF-SCHEMATIC-DROP). Unlike every other dialog it cannot
+// be dismissed: clicking an option is the only way out, so getChosenIndex() always names
+// an option the player picked, and it only ever finishes Accepted. It inherits the base's
+// refusal of Q and of a click outside (ModalDialog::isDismissible) and adds the refusal
+// of Escape below.
+class SchematicChoiceDialog : public ModalDialog
 {
     Q_OBJECT
 
@@ -30,9 +31,8 @@ public:
 public slots:
     // Refuses the dismissal (REQ-DEF-SCHEMATIC-DROP): the drop is a reward the player
     // has earned, and leaving without choosing would either forfeit it or award the
-    // option that happens to be first. Escape, Alt+F4, and the window manager's close
-    // all funnel through QDialog::reject(), so declining it here turns away every one of
-    // them at once rather than swallowing keys one at a time.
+    // option that happens to be first. Escape funnels through QDialog::reject(), so
+    // declining it here turns it away without swallowing keys one at a time.
     void reject() override;
 
 private: