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/renderer/editor/state/projectState.ts

@@ -350,6 +350,7 @@ export function useProjectState(licenseActive: boolean, opts?: ProjectStateOpts)
             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: [],
@@ -591,6 +592,7 @@ export function useProjectState(licenseActive: boolean, opts?: ProjectStateOpts)
             : null),
           ...(patch.darkenScene !== undefined ? { darkenScene: patch.darkenScene } : null),
           ...(patch.traps !== undefined ? { traps: patch.traps } : null),
+          ...(patch.grid !== undefined ? { grid: patch.grid } : null),
           ...(patch.settings ? { settings: { ...scene.settings, ...patch.settings } } : null),
           ...(patch.media ? { media: { ...scene.media, ...patch.media } } : null),
           layout: patch.layout ? { ...scene.layout, ...patch.layout } : scene.layout,