refactor(telegram): optimize message handling and unify system context

- handler.py: Cleaned up. All functions and imports are now actively used.

- _enqueue_user_message: Refactored to handle both messages and callback queries, eliminating duplicate building logic.

- _20_telegram_context.py: Now the single source of truth for injecting agent_instructions and system_context_reply.

- File Cleanup: Deleted unused fw.telegram.system_context.md and fw.telegram.cleared.md.

- fix: Corrected bot invocation logic within group chats.

plugins/_telegram_integration/extensions/python/tool_execute_after/_50_telegram_response.py

@@ -1,5 +1,4 @@
 from helpers.extension import Extension
-from helpers.print_style import PrintStyle
 from helpers.tool import Response
 from plugins._telegram_integration.helpers.handler import (
     CTX_TG_BOT,