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');
+  });
 });

src/channels/slack/adapter.ts

@@ -22,6 +22,8 @@ export interface SlackAdapterConfig {
   signingSecret: string;
   /** Channel IDs to respond in. Empty = all channels. */
   allowedChannelIds?: string[];
+  /** Require bot mention to respond (default: false). */
+  requireMention?: boolean;
 }
 
 /** Minimal shape of a Slack message event from Bolt. */
@@ -49,6 +51,7 @@ export class SlackAdapter implements ChannelAdapter {
   private messageHandler?: (msg: InboundMessage) => void;
   private config: SlackAdapterConfig;
   private userNameCache: Map<string, string> = new Map();
+  private botUserId?: string;
 
   get status(): ChannelStatus {
     return this._status;
@@ -81,6 +84,15 @@ export class SlackAdapter implements ChannelAdapter {
       });
 
       await this.app.start();
+
+      // Resolve bot user ID for mention detection
+      try {
+        const authResult = await this.app.client.auth.test();
+        this.botUserId = authResult.user_id as string | undefined;
+      } catch {
+        console.warn('Slack: could not resolve bot user ID for mention detection');
+      }
+
       this._status = 'connected';
       console.log('Slack bot connected via Socket Mode');
     } catch (error) {
@@ -167,6 +179,15 @@ export class SlackAdapter implements ChannelAdapter {
       return;
     }
 
+    // Mention requirement
+    const requireMention = this.config.requireMention ?? false;
+    if (requireMention && this.botUserId) {
+      const mentionPattern = `<@${this.botUserId}>`;
+      if (!(message.text ?? '').includes(mentionPattern)) {
+        return;
+      }
+    }
+
     // Build peer ID: channelId:threadTs (thread-aware)
     const threadTs = message.thread_ts ?? message.ts ?? '';
     const peerId = `${channelId}:${threadTs}`;