feat(msteams): add per-channel requireMention config

- Add teams/channels config structure to MSTeamsConfig
- Implement requireMention check in monitor.ts
  - Resolution order: channel > team > global > default (true)
- Update zod schema for validation
- Document RSC permissions for receiving all messages without @mention
- Document Graph API Proxy pattern for historical message access
- Document private channel limitations
- Document team/channel ID format (use URL path, not groupId)

src/msteams/monitor.ts

@@ -57,6 +57,12 @@ type TeamsActivity = {
     type?: string;
     mentioned?: { id?: string; name?: string };
   }>;
+  /** Teams-specific channel data including team info */
+  channelData?: {
+    team?: { id?: string; name?: string };
+    channel?: { id?: string; name?: string };
+    tenant?: { id?: string };
+  };
 };
 
 type TeamsTurnContext = {
@@ -288,6 +294,34 @@ export async function monitorMSTeamsProvider(
       }
     }
 
+    // Check requireMention for channels and group chats
+    if (!isDirectMessage) {
+      const teamId = activity.channelData?.team?.id;
+      const channelId = conversationId;
+
+      // Resolution order: channel config > team config > global config > default (true)
+      const teamConfig = teamId ? msteamsCfg?.teams?.[teamId] : undefined;
+      const channelConfig = teamConfig?.channels?.[channelId];
+
+      const requireMention =
+        channelConfig?.requireMention ??
+        teamConfig?.requireMention ??
+        msteamsCfg?.requireMention ??
+        true;
+
+      const mentioned = wasBotMentioned(activity);
+
+      if (requireMention && !mentioned) {
+        log.debug("skipping message (mention required)", {
+          teamId,
+          channelId,
+          requireMention,
+          mentioned,
+        });
+        return;
+      }
+    }
+
     // Format the message body with envelope
     const timestamp = parseTimestamp(activity.timestamp);
     const body = formatAgentEnvelope({