Add home button to question screen toolbar to exit the run

Previously the only way out of an active question run was Escape to
open the pause overlay, then click Exit Run. Exposes main.gd's exit
logic publicly (_exit_run -> exit_current_run) so a house-icon button
in the question toolbar can trigger it directly.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

scripts/ui/main.gd

@@ -896,7 +896,7 @@ func _build_app_menu() -> void:
 	menu_exit_button.text = "Exit Run"
 	menu_exit_button.custom_minimum_size = Vector2(0, 48)
 	UISoundService.set_button_sound(menu_exit_button, "back")
-	menu_exit_button.pressed.connect(_exit_run)
+	menu_exit_button.pressed.connect(exit_current_run)
 	content.add_child(menu_exit_button)
 
 	var logout := Button.new()
@@ -943,7 +943,7 @@ func _navigate_from_pause(target_screen: String) -> void:
 		BlockSessionService.pause_current_question_timer()
 
 
-func _exit_run() -> void:
+func exit_current_run() -> void:
 	_close_app_menu()
 	if current_screen_name == "ccs_player":
 		var ccs_player = screens.get("ccs_player")