Telegram Channels plugin drops messages when LLM is busy

Description

When using the Telegram Channels plugin, incoming messages are silently dropped if the LLM is currently processing another message. The user receives "LLM request rejected: You're out of extra usage" on Telegram, which is misleading — the actual issue is that the session is busy, not that the subscription quota is exhausted.

Steps to reproduce

1. Set up Telegram Channels plugin with a bot
2. Send a message → bot starts processing/responding
3. While the bot is generating a response, send another message
4. The second message is dropped with "LLM request rejected" error shown to the Telegram user

Also reproduced:

• Sending messages in quick succession (< 2 seconds apart)
• Sending a message right after the bot finishes replying (internal processing not yet complete)

Expected behavior

• Incoming messages should be queued when the LLM is busy
• Queued messages should be processed after the current response completes
• Messages should never be silently dropped

Actual behavior

• Messages sent while LLM is busy are rejected immediately
• The Telegram user sees "LLM request rejected: You're out of extra usage. Add more at claude.ai/settings/usage and keep going." which is misleading (subscription is Max/unlimited)
• No retry or queue mechanism exists
• Messages are permanently lost

Impact

For users running Claude Code as an always-on Telegram assistant, this means:

• Rapid messages are lost
• Users must wait and guess when the bot is "ready" before sending
• The misleading error message causes confusion about subscription status
• No indication to the user that their message was dropped vs. being processed

Suggested fix

Add a message queue in the Channels plugin that buffers incoming messages when the LLM is busy, and processes them sequentially once the current response completes.

Environment

• Claude Code version: latest
• OS: macOS (Darwin 25.2.0)
• Subscription: Max (unlimited)
• Plugin: Telegram Channels (plugin:telegram:telegram)