feat: add group chat and mention-gating to channel adapters

Slack: add requireMention option, resolve bot user ID on connect.
Telegram: add group chat mention/reply-to-bot detection, strip @mention
from message text, default requireMention=true for groups.
WhatsApp: add allowedGroupIds for group chat support, mention detection
via mentionedIds and body text, strip bot mention from messages.

src/channels/slack/adapter.test.ts

@@ -7,6 +7,9 @@ const mockPostMessage = vi.fn();
 const mockStart = vi.fn();
 const mockStop = vi.fn();
 
+const mockAuthTest = vi.fn().mockResolvedValue({ user_id: 'UBOT123' });
+const mockUsersInfo = vi.fn().mockResolvedValue({ user: { real_name: 'Test User', name: 'testuser' } });
+
 /** Create a fresh mock Bolt App instance. */
 function createMockApp() {
   capturedMessageHandler = null;
@@ -20,6 +23,12 @@ function createMockApp() {
       chat: {
         postMessage: mockPostMessage,
       },
+      auth: {
+        test: mockAuthTest,
+      },
+      users: {
+        info: mockUsersInfo,
+      },
     },
   };
 }
@@ -172,7 +181,7 @@ describe('SlackAdapter', () => {
     const msg: InboundMessage = handler.mock.calls[0][0];
     expect(msg.channel).toBe('slack');
     expect(msg.senderId).toBe('C123:1111.0000');
-    expect(msg.senderName).toBe('U456');
+    expect(msg.senderName).toBe('Test User');
     expect(msg.text).toBe('Hello Flynn');
     expect(msg.id).toBe('1234.5678');
   });
@@ -374,4 +383,66 @@ describe('SlackAdapter', () => {
     const msg: InboundMessage = handler.mock.calls[0][0];
     expect(msg.text).toBe('Hello');
   });
+
+  // ── Mention gating ─────────────────────────────────────────────
+
+  it('ignores messages without mention when requireMention is true', async () => {
+    const mentionAdapter = new SlackAdapter({
+      ...baseConfig,
+      requireMention: true,
+    });
+    const handler = vi.fn();
+    mentionAdapter.onMessage(handler);
+
+    await mentionAdapter.connect();
+
+    await simulateMessage({
+      ts: '1234.5678',
+      channel: 'C123',
+      user: 'U456',
+      text: 'Hello everyone',
+    });
+
+    expect(handler).not.toHaveBeenCalled();
+  });
+
+  it('processes messages with bot mention when requireMention is true', async () => {
+    const mentionAdapter = new SlackAdapter({
+      ...baseConfig,
+      requireMention: true,
+    });
+    const handler = vi.fn();
+    mentionAdapter.onMessage(handler);
+
+    await mentionAdapter.connect();
+
+    await simulateMessage({
+      ts: '1234.5678',
+      channel: 'C123',
+      user: 'U456',
+      text: '<@UBOT123> What is the weather?',
+    });
+
+    expect(handler).toHaveBeenCalledTimes(1);
+    const msg: InboundMessage = handler.mock.calls[0][0];
+    expect(msg.text).toBe('What is the weather?');
+  });
+
+  it('processes all messages when requireMention is false (default)', async () => {
+    const handler = vi.fn();
+    adapter.onMessage(handler);
+
+    await adapter.connect();
+
+    await simulateMessage({
+      ts: '1234.5678',
+      channel: 'C123',
+      user: 'U456',
+      text: 'Hello without mention',
+    });
+
+    expect(handler).toHaveBeenCalledTimes(1);
+    const msg: InboundMessage = handler.mock.calls[0][0];
+    expect(msg.text).toBe('Hello without mention');
+  });
 });