Add demolish-mode vignette border (REQ-UI-DEMOLISH-BORDER)

Extract the mitred picture-frame vignette from drawPauseBorder into a shared
drawVignetteBorder(edgeColor) helper, and draw a second vignette while
demolish mode is active, tinted with visuals.toml [overlays].demolish_tint
(including its configured alpha) instead of black. Both vignettes compose
when the game is paused and in demolish mode at once.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Y7N59FsLA5e2kuVdqe4Uhc

src/ui/GameWorldView.cpp

@@ -433,6 +433,7 @@ void GameWorldView::paintGL()
     drawOverlays(painter);
     drawScreenSpace(painter);
     drawPauseBorder(painter);
+    drawDemolishBorder(painter);
     drawReplayOverlay(painter);
 }
 
@@ -1700,15 +1701,27 @@ void GameWorldView::drawScreenSpace(QPainter& /*painter*/)
 void GameWorldView::drawPauseBorder(QPainter& painter)
 {
     if (m_gameSpeedMultiplier > 0.0) { return; }
+    drawVignetteBorder(painter, QColor(0, 0, 0, 128));   // 50% black at the edge
+}
 
+void GameWorldView::drawDemolishBorder(QPainter& painter)
+{
+    if (!m_demolishMode) { return; }
+    // Reuse the demolish overlay color (with its configured alpha) as the edge color.
+    drawVignetteBorder(painter, m_visuals->overlays.demolishTint);
+}
+
+void GameWorldView::drawVignetteBorder(QPainter& painter, const QColor& edgeColor)
+{
     // Border thickness in pixels, capped so it never exceeds half the viewport on
-    // very small windows (which would leave no un-darkened center).
+    // very small windows (which would leave no un-tinted center).
     const qreal borderPx = std::min<qreal>(
         100.0, std::min(width(), height()) / 2.0);
     if (borderPx <= 0.0) { return; }
 
-    const QColor edge(0, 0, 0, 128);        // 50% black at the viewport edge
+    const QColor& edge = edgeColor;         // full color (and alpha) at the viewport edge
-    const QColor inner(0, 0, 0, 0);         // fully transparent toward the center
+    QColor inner = edgeColor;
+    inner.setAlpha(0);                      // same color, fully transparent toward the center
 
     const qreal w = width();
     const qreal h = height();

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
+    // Vignette-style border shown while the game is paused (speed 0x, REQ-UI-PAUSE-BORDER)
-    // paused state hard to miss: a black frame whose alpha fades from 50% at the
+    // to make the paused state hard to miss: a black frame whose alpha fades from 50% at
-    // viewport edges to 0% toward the center.
+    // 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;