Introduce file picker and GUI configuration with enhancements.

- Add visual file picker for GUI with toggle support.
- Introduce `GUIConfig` class for loading GUI settings from configuration file.
- Refactor window initialization to support dynamic sizing based on configuration.
- Add macOS-specific handling for fullscreen behavior.
- Improve header inclusion order and minor code cleanup.

KKeymap.cc

@@ -1,9 +1,9 @@
-#include "KKeymap.h"
-
 #include <iostream>
 #include <ncurses.h>
 #include <ostream>
 
+#include "KKeymap.h"
+
 
 auto
 KLookupKCommand(const int ascii_key, const bool ctrl, CommandId &out) -> bool
@@ -83,6 +83,9 @@ KLookupKCommand(const int ascii_key, const bool ctrl, CommandId &out) -> bool
 	case 'u':
 		out = CommandId::Undo;
 		return true;
+	case 'v':
+		out = CommandId::VisualFilePickerToggle;
+		return true;
 	case 'w':
 		out = CommandId::ShowWorkingDirectory;
 		return true;