feat: add user-configurable notification settings (#601)

apps/x/packages/shared/src/notification-settings.ts

@@ -0,0 +1,36 @@
+import { z } from 'zod';
+
+/**
+ * Notification categories the user can independently toggle.
+ *
+ * - chat_completion:  an agent finished generating a response
+ * - new_email:        a new email arrived during incremental Gmail sync
+ * - agent_permission: an agent is requesting permission to run a tool
+ */
+export const NotificationCategorySchema = z.enum([
+  'chat_completion',
+  'new_email',
+  'agent_permission',
+]);
+
+export const NotificationCategoriesSchema = z.object({
+  chat_completion: z.boolean(),
+  new_email: z.boolean(),
+  agent_permission: z.boolean(),
+});
+
+export const NotificationSettingsSchema = z.object({
+  categories: NotificationCategoriesSchema,
+});
+
+export const DEFAULT_NOTIFICATION_SETTINGS: NotificationSettings = {
+  categories: {
+    chat_completion: true,
+    new_email: true,
+    agent_permission: true,
+  },
+};
+
+export type NotificationCategory = z.infer<typeof NotificationCategorySchema>;
+export type NotificationCategories = z.infer<typeof NotificationCategoriesSchema>;
+export type NotificationSettings = z.infer<typeof NotificationSettingsSchema>;