feat: save games and edit scene darkness

Persist show state to local saves; author map darkness in scene editor with bake-to-scene and help updates.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/renderer/sceneEditor/SceneEditorApp.module.css

@@ -86,6 +86,39 @@
   user-select: none;
 }
 
+.darknessTools {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 8px;
+  align-items: center;
+}
+
+.darknessBrushLayer {
+  position: absolute;
+  z-index: 29;
+  cursor: none;
+  touch-action: none;
+}
+
+.brushCursor {
+  position: absolute;
+  z-index: 30;
+  will-change: left, top;
+  transform: translate(-50%, -50%);
+  border-radius: 50%;
+  border: 1px solid rgba(255, 255, 255, 0.55);
+  box-shadow:
+    0 0 0 1px rgba(0, 0, 0, 0.3),
+    0 0 18px rgba(255, 140, 40, 0.12),
+    inset 0 0 18px rgba(255, 140, 40, 0.1);
+  background: rgba(255, 160, 60, 0.03);
+  pointer-events: none;
+}
+
+.brushCursorSquare {
+  border-radius: 2px;
+}
+
 .field {
   display: grid;
   gap: 6px;