feat(agent-browser): add opt-in preview data injection

electron/services/preview-data-session.ts

@@ -62,6 +62,10 @@ export type PreviewDataSessionInvalidationReason =
   | 'replaced'
   | 'manual';
 
+export type PreviewDataSessionInvalidationListener = (
+  reason: PreviewDataSessionInvalidationReason,
+) => void;
+
 export type PreviewDataSessionOpenInput = {
   projectPath: string;
   origin: string;
@@ -232,6 +236,7 @@ export class PreviewDataSessionManager {
   private readonly getAccountBinding: typeof getWorksSquareAccountBinding;
   private readonly isCurrentAccountBinding: typeof isCurrentWorksSquareAccountBinding;
   private readonly unsubscribeWorksSession: () => void;
+  private readonly invalidationListeners = new Set<PreviewDataSessionInvalidationListener>();
   private session: InternalSession | null = null;
   private boundAccountBinding: WorksSquareAccountBinding | null;
   private disposed = false;
@@ -285,6 +290,7 @@ export class PreviewDataSessionManager {
       throw new PreviewDataSessionError('runtime_unavailable', 'Preview data runtime is unavailable');
     }
     const token = tokenBytes.toString('base64url');
+    this.invalidate('replaced');
     const snapshot: PreviewDataSessionSnapshot = Object.freeze({
       projectPath: active.path,
       projectId: active.projectId,
@@ -307,6 +313,14 @@ export class PreviewDataSessionManager {
     return this.session?.snapshot ?? null;
   }
 
+  subscribeInvalidation(listener: PreviewDataSessionInvalidationListener): () => void {
+    if (this.disposed) return () => undefined;
+    this.invalidationListeners.add(listener);
+    return () => {
+      this.invalidationListeners.delete(listener);
+    };
+  }
+
   getInjectionValue(hostPort = this.hostPort): PreviewDataInjectionValue | null {
     const session = this.session;
     if (!session || !Number.isSafeInteger(hostPort) || hostPort < 1 || hostPort > 65_535) {
@@ -409,8 +423,16 @@ export class PreviewDataSessionManager {
     }
   }
 
-  invalidate(_reason: PreviewDataSessionInvalidationReason = 'manual'): void {
+  invalidate(reason: PreviewDataSessionInvalidationReason = 'manual'): void {
+    if (!this.session) return;
     this.session = null;
+    for (const listener of this.invalidationListeners) {
+      try {
+        listener(reason);
+      } catch {
+        // A browser cleanup observer must not interrupt token invalidation.
+      }
+    }
   }
 
   dispose(): void {
@@ -418,6 +440,7 @@ export class PreviewDataSessionManager {
     this.disposed = true;
     this.invalidate('main_shutdown');
     this.unsubscribeWorksSession();
+    this.invalidationListeners.clear();
   }
 }