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/main/index.ts

@@ -1,6 +1,7 @@
 import { app, BrowserWindow, dialog, Menu, protocol } from 'electron';
 
 import { ipcChannels, type SessionState } from '../shared/ipc/contracts';
+import type { Project } from '../shared/types';
 import {
   PROJECT_ZIP_OPEN_DIALOG_FILTER,
   PROJECT_ZIP_SAVE_DIALOG_FILTER,
@@ -11,6 +12,7 @@ import {
 } from '../shared/project/projectZipExtension';
 
 import { EffectsStore } from './effects/effectsStore';
+import { SceneDarknessStore } from './effects/sceneDarknessStore';
 import { installIpcRouter, registerHandler, setLicenseAssert } from './ipc/router';
 import { LicenseService } from './license/licenseService';
 import { ZipProjectStore } from './project/zipStore';
@@ -117,6 +119,7 @@ function installAppMenuForSession(): void {
 }
 
 const effectsStore = new EffectsStore();
+const sceneDarknessStore = new SceneDarknessStore();
 const videoStore = new VideoPlaybackStore();
 
 function emitEffectsState(): void {
@@ -126,6 +129,20 @@ function emitEffectsState(): void {
   }
 }
 
+function emitSceneDarknessState(): void {
+  const state = sceneDarknessStore.getState();
+  for (const win of BrowserWindow.getAllWindows()) {
+    win.webContents.send(ipcChannels.sceneDarkness.stateChanged, { state });
+  }
+}
+
+function syncSceneDarknessForProject(project: Project): void {
+  const cacheKey = project.currentGraphNodeId ?? project.currentSceneId ?? null;
+  const scene = project.currentSceneId ? project.scenes[project.currentSceneId] : undefined;
+  const enabled = Boolean(scene?.darkenScene) && scene?.previewAssetType === 'image';
+  sceneDarknessStore.switchScene(cacheKey, enabled);
+}
+
 function emitVideoState(): void {
   const state = videoStore.getState();
   for (const win of BrowserWindow.getAllWindows()) {
@@ -267,7 +284,11 @@ async function main() {
   registerHandler(ipcChannels.license.clearToken, () => licenseService.clearToken());
   registerHandler(ipcChannels.license.acceptEula, ({ version }) => licenseService.acceptEula(version));
   registerHandler(ipcChannels.windows.openMultiWindow, () => {
+    sceneDarknessStore.resetSession();
     openMultiWindow();
+    const project = projectStore.getOpenProject();
+    if (project) syncSceneDarknessForProject(project);
+    emitSceneDarknessState();
     return { ok: true };
   });
   registerHandler(ipcChannels.windows.closeMultiWindow, () => {
@@ -303,6 +324,15 @@ async function main() {
     emitSessionState();
     return { project };
   });
+  registerHandler(ipcChannels.project.close, async () => {
+    await projectStore.closeOpenProject();
+    effectsStore.clear();
+    sceneDarknessStore.resetSession();
+    emitEffectsState();
+    emitSceneDarknessState();
+    emitSessionState();
+    return { ok: true };
+  });
   registerHandler(ipcChannels.project.get, () => {
     return { project: projectStore.getOpenProject() };
   });
@@ -313,7 +343,10 @@ async function main() {
   registerHandler(ipcChannels.project.setCurrentScene, async ({ sceneId }) => {
     await projectStore.updateProject((p) => ({ ...p, currentSceneId: sceneId, currentGraphNodeId: null }));
     effectsStore.clear();
+    const project = projectStore.getOpenProject();
+    if (project) syncSceneDarknessForProject(project);
     emitEffectsState();
+    emitSceneDarknessState();
     emitSessionState();
     return { currentSceneId: projectStore.getOpenProject()?.currentSceneId ?? null };
   });
@@ -327,7 +360,10 @@ async function main() {
       currentSceneId: gn ? gn.sceneId : null,
     }));
     effectsStore.clear();
+    const project = projectStore.getOpenProject();
+    if (project) syncSceneDarknessForProject(project);
     emitEffectsState();
+    emitSceneDarknessState();
     emitSessionState();
     const p = projectStore.getOpenProject();
     return {
@@ -337,6 +373,11 @@ async function main() {
   });
   registerHandler(ipcChannels.project.updateScene, async ({ sceneId, patch }) => {
     const next = await projectStore.updateScene(sceneId, patch);
+    const project = projectStore.getOpenProject();
+    if (project && project.currentSceneId === sceneId && patch.darkenScene !== undefined) {
+      syncSceneDarknessForProject(project);
+      emitSceneDarknessState();
+    }
     emitSessionState();
     return { scene: next };
   });
@@ -524,6 +565,15 @@ async function main() {
     return { ok: true };
   });
 
+  registerHandler(ipcChannels.sceneDarkness.getState, () => {
+    return { state: sceneDarknessStore.getState() };
+  });
+  registerHandler(ipcChannels.sceneDarkness.dispatch, ({ event }) => {
+    sceneDarknessStore.dispatch(event);
+    emitSceneDarknessState();
+    return { ok: true };
+  });
+
   registerHandler(ipcChannels.video.getState, () => {
     return { state: videoStore.getState() };
   });