feat(scenes): add scene darkness reveal and fix project reopen crash

Add darkenScene with Opening brush in presentation, persist reveal strokes per scene during a session, and close projects properly on return to home. Harden dnd asset streaming to avoid Windows main-process crashes when reopening projects.

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

app/shared/types/domain.ts

@@ -90,6 +90,8 @@ export type Scene = {
   previewVideoAutostart: boolean;
   /** Поворот превью в градусах (0/90/180/270). */
   previewRotationDeg: 0 | 90 | 180 | 270;
+  /** В режиме показа: сцена начинается полностью затемнённой; мастер «раскрывает» кистью. */
+  darkenScene: boolean;
   media: SceneMediaRefs;
   settings: SceneSettings;
   connections: SceneId[];

app/shared/types/effects.ts

@@ -8,6 +8,7 @@ export type EffectToolType =
   | 'sunbeam'
   | 'poisonCloud'
   | 'freeze'
+  | 'exploreBrush'
   | 'eraser';
 
 export type EffectInstanceType =

app/shared/types/index.ts

@@ -1,4 +1,5 @@
 export * from './domain';
 export * from './effects';
 export * from './ids';
+export * from './sceneDarkness';
 export * from './videoPlayback';

app/shared/types/sceneDarkness.ts

@@ -0,0 +1,22 @@
+import type { NPoint } from './effects';
+
+export type SceneDarknessRevealStroke = {
+  id: string;
+  seed: number;
+  createdAtMs: number;
+  points: NPoint[];
+  radiusN: number;
+};
+
+export type SceneDarknessState = {
+  revision: number;
+  /** Текущая сцена помечена «Затемнить сцену» (только для изображений). */
+  enabled: boolean;
+  cacheKey: string | null;
+  strokes: SceneDarknessRevealStroke[];
+  draft: { points: NPoint[]; radiusN: number } | null;
+};
+
+export type SceneDarknessEvent =
+  | { kind: 'draft.set'; draft: { points: NPoint[]; radiusN: number } | null }
+  | { kind: 'stroke.add'; stroke: SceneDarknessRevealStroke };