feat: add /newchat command and topic precheck for groups

[BukeLy]

Summary

• Add /newchat <prompts> local command to create new Topic and send first message to Agent
• Add topic precheck when bot joins authorized groups (checks is_forum and can_manage_topics)
• Send detailed setup instructions if precheck fails

Test plan

• Deploy and test /newchat 你好 in a group with Topics enabled
• Add bot to a group without Topics enabled, verify precheck notification
• Add bot to a group without Topic management permission, verify permission notification
• Check CloudWatch Logs for any errors

[Copilot]

Pull request overview

This PR adds a /newchat command that creates forum topics and sends the first message to an agent, and implements a precheck system to verify groups have Topics enabled and appropriate permissions when the bot joins.

Changes:

• Added /newchat <prompts> command to create a new forum topic and send the first message to the agent
• Added topic precheck when bot joins authorized groups to validate forum settings and permissions
• Modified consumer to handle special is_newchat message format

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 11 comments.

File	Description
agent-sdk-client/handler.py	Implements /newchat command handler, forum requirements checker, and topic precheck logic on bot join
agent-sdk-client/consumer.py	Refactored to handle both regular messages and newchat messages with different data structures
agent-sdk-client/config.toml	Added /newchat to local_commands configuration

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[Copilot]

The comments "newchat 消息直接使用 message_data" and "正常消息解析 Update" are in Chinese, while most other comments in the codebase are in English. For consistency and maintainability, consider using English for all code comments.

Suggested change

	# newchat 消息直接使用 message_data
	chat_id = message_data['chat_id']
	thread_id = message_data['thread_id']
	user_message = message_data['text']
	message_id = message_data.get('message_id')
	else:
	# 正常消息解析 Update
	# For new chat messages, use message_data directly
	chat_id = message_data['chat_id']
	thread_id = message_data['thread_id']
	user_message = message_data['text']
	message_id = message_data.get('message_id')
	else:
	# For regular messages, parse the Telegram Update

[Copilot]

The config.toml adds /newchat as a local command with response "创建新对话", but /newchat is not actually a local command - it requires async processing and SQS messaging. This is inconsistent with the implementation in handler.py where /newchat is handled specially before the local command check. The entry in local_commands may cause confusion or incorrect behavior if config.is_local_command() is called for /newchat. Consider removing this entry from local_commands or documenting why it's included.

Suggested change

newchat = "创建新对话"