feat(permissions): richer channel-approval flow with agent selection and free-text naming

Replace the hardcoded Approve/Ignore card with a multi-step flow:
- Single agent: "Connect to [name]" / "Connect new agent" / "Reject"
- Multiple agents: "Choose existing agent" (follow-up list) / "Connect new agent" / "Reject"
- "Connect new agent" prompts for a free-text name via DM, creates immediately on reply
- Add setMessageInterceptor router hook for capturing free-text replies
- Add resolveChannelName optional method to ChannelAdapter interface

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/channels/adapter.ts

@@ -135,6 +135,7 @@ export interface ChannelAdapter {
   // Optional
   setTyping?(platformId: string, threadId: string | null): Promise<void>;
   syncConversations?(): Promise<ConversationInfo[]>;
+  resolveChannelName?(platformId: string): Promise<string | null>;
 
   /**
    * Subscribe the bot to a thread so follow-up messages route via the