feat(scene): battle grid overlay with color and trap VFX stacking

Add configurable square/hex grid in the scene editor (persisted and shown on control/presentation) and keep trap activation effects above trap icons.

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

app/shared/graph/sceneListOrder.test.ts

@@ -23,6 +23,7 @@ function scene(id: string): Scene {
     previewRotationDeg: 0,
     darkenScene: false,
     traps: [],
+    grid: { enabled: false, type: 'square', sizeN: 0.06, color: '#ffffff' },
     media: { videos: [], audios: [] },
     settings: { autoplayVideo: false, autoplayAudio: true, loopVideo: true, loopAudio: true },
     connections: [],

app/shared/graph/storylineExportImport.test.ts

@@ -28,6 +28,7 @@ function scene(id: string, title: string): Scene {
     previewRotationDeg: 0,
     darkenScene: false,
     traps: [],
+    grid: { enabled: false, type: 'square', sizeN: 0.06, color: '#ffffff' },
     media: { videos: [], audios: [] },
     settings: { autoplayVideo: false, autoplayAudio: false, loopVideo: false, loopAudio: false },
     connections: [],