fix: resolve whatsapp-web.js ESM import for Node.js v25

whatsapp-web.js lacks proper ESM named exports, causing SyntaxError on
import. Switch to default import with destructuring, use InstanceType
for the Client type annotation, and update test mock to provide both
default and named exports.

src/channels/whatsapp/adapter.test.ts

@@ -32,13 +32,19 @@ function createMockClient() {
 
 let mockClient = createMockClient();
 
-vi.mock('whatsapp-web.js', () => ({
-  Client: vi.fn().mockImplementation(() => mockClient),
-  LocalAuth: vi.fn().mockImplementation((opts: Record<string, unknown>) => ({
+vi.mock('whatsapp-web.js', () => {
+  const Client = vi.fn().mockImplementation(() => mockClient);
+  const LocalAuth = vi.fn().mockImplementation((opts: Record<string, unknown>) => ({
     type: 'local',
     ...opts,
-  })),
-}));
+  }));
+  return {
+    default: { Client, LocalAuth, MessageMedia: vi.fn() },
+    Client,
+    LocalAuth,
+    MessageMedia: vi.fn(),
+  };
+});
 
 import { WhatsAppAdapter, type WhatsAppAdapterConfig } from './adapter.js';
 import type { InboundMessage } from '../types.js';

src/channels/whatsapp/adapter.ts

@@ -7,7 +7,8 @@
  * Messages are chunked at 4096 chars (same as Telegram).
  */
 
-import { Client, LocalAuth, MessageMedia } from 'whatsapp-web.js';
+import WhatsApp from 'whatsapp-web.js';
+const { Client, LocalAuth, MessageMedia } = WhatsApp;
 import type {
   Attachment,
   InboundMessage,
@@ -57,7 +58,7 @@ export class WhatsAppAdapter implements ChannelAdapter {
   readonly name = 'whatsapp';
 
   private _status: ChannelStatus = 'disconnected';
-  private client: Client | null = null;
+  private client: InstanceType<typeof Client> | null = null;
   private messageHandler?: (msg: InboundMessage) => void;
   private config: WhatsAppAdapterConfig;
   private botId?: string;