refactor(command-system): standardize command execution with *args/**kwargs

- 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

plugins/code/autopairs/__init__.py

@@ -0,0 +1,3 @@
+"""
+    Plugin Module
+"""