Add Octo user file delivery for Telegram and WhatsApp

[pmbstyle]

Summary

• add a new send_file_to_user tool that can send a workspace file or download a URL before sending
• wire channel-specific file delivery for Telegram and WhatsApp, including a WhatsApp bridge /send-file endpoint
• keep the tool octo-only and add tests for tool behavior and worker restrictions

Testing

• uv run pytest tests/test_send_file_to_user_tool.py tests/test_whatsapp_runtime.py tests/test_connector_tools.py tests/test_octo_runtime_contracts.py tests/test_tool_profiles.py -q
• uv run pytest tests/test_runtime_mcp_integration.py tests/test_connector_tools.py tests/test_send_file_to_user_tool.py -q