fix: refactor TUI to use dispatcher pattern

Co-authored-by: aider (deepseek/deepseek-coder) <aider@aider.chat>

tui.h

@@ -2,6 +2,7 @@
 #define TUI_H
 
 #include "engine.h"
+#include "dispatcher.h"
 
 // Initialize TUI
 void tui_init(Engine *engine);
@@ -12,7 +13,4 @@ void tui_run(Engine *engine);
 // Cleanup TUI
 void tui_cleanup(void);
 
-// Handle command mode input (after pressing ':')
-void tui_handle_command_mode(Engine *engine);
-
 #endif // TUI_H