- Remove tabs controller, tab widget, and tabs widget files and move to plugin
- Delete plugins/README.txt
- Add register_controller method to controller system for plugin use
- Add error handling for plugin crashes via futures callback
- Refactor exec_with_args to use *args/**kwargs instead of tuple arguments
- Add *args/**kwargs to all command execute functions for consistency
- Support multiple key bindings per command in registration
- Add character-based key binding support via get_char() in KeyMapper
- Make execute_plugin async and use asyncio.run for plugin execution
- Use MIME type from Gio content_type instead of language for ftype
