Make params optional in McpUiInitializedNotificationSchema

Notifications sent without params (e.g., `{ method: "ui/notifications/initialized" }`)
were being rejected by the schema validation because params was required.
This makes params optional so notifications without explicit params are accepted.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/types.ts

@@ -221,7 +221,7 @@ export type McpUiInitializeResult = z.infer<typeof McpUiInitializeResultSchema>;
 
 export const McpUiInitializedNotificationSchema = z.object({
   method: z.literal("ui/notifications/initialized"),
-  params: z.object({}),
+  params: z.object({}).optional(),
 });
 export type McpUiInitializedNotification = z.infer<
   typeof McpUiInitializedNotificationSchema