Add demolish-mode vignette

src/ui/GameWorldView.h

@@ -131,10 +131,18 @@ private:
     void drawBeams(QPainter& painter);
     void drawOverlays(QPainter& painter);
     void drawScreenSpace(QPainter& painter);
-    // Vignette-style border shown while the game is paused (speed 0x) to make the
-    // paused state hard to miss: a black frame whose alpha fades from 50% at the
-    // viewport edges to 0% toward the center.
+    // Vignette-style border shown while the game is paused (speed 0x, REQ-UI-PAUSE-BORDER)
+    // to make the paused state hard to miss: a black frame whose alpha fades from 50% at
+    // the viewport edges to 0% toward the center.
     void drawPauseBorder(QPainter& painter);
+    // Vignette-style border shown while demolish mode is active (REQ-UI-DEMOLISH-BORDER),
+    // tinted with the demolish overlay color (including its configured alpha) from
+    // visuals.toml instead of black.
+    void drawDemolishBorder(QPainter& painter);
+    // Shared drawing for the pause/demolish vignettes: a mitred picture-frame border
+    // whose alpha fades from `edgeColor` (with its own alpha) at the viewport edge to
+    // fully transparent toward the center.
+    void drawVignetteBorder(QPainter& painter, const QColor& edgeColor);
     void drawReplayOverlay(QPainter& painter);
 
     float    getTilePx() const;