Add wrapping keyboard and gamepad focus rings

- Link every modal's enabled controls into a wrapping UiFocus ring and give each screen a default focus target.
- Add gamepad A/B bindings for ui_accept/ui_cancel; include Start menu footer actions and Continue in its focus ring.
- Skip hidden/disabled controls, close focus traps via per-modal cancel behavior, and return review to the menu on cancel.
- Record the focus audit and add regression coverage.

src/test/tests/test_ui_buttons.gd

@@ -4,6 +4,7 @@ extends RefCounted
 ## theme when a control is focused or disabled.
 
 const UiStyles := preload("res://src/game/ui/ui_styles.gd")
+const UiFocus := preload("res://src/game/ui/ui_focus.gd")
 
 func test_shared_button_states_are_complete() -> bool:
 	var button := Button.new()
@@ -24,3 +25,16 @@ func test_shared_button_states_are_complete() -> bool:
 		"the disabled state is visually distinct from normal")
 	button.free()
 	return a and b and c
+
+func test_focus_helper_skips_hidden_and_disabled_controls() -> bool:
+	var hidden := Button.new()
+	hidden.visible = false
+	var disabled := Button.new()
+	disabled.disabled = true
+	var normal := Button.new()
+	var first := UiFocus.first_enabled([hidden, disabled, normal])
+	var a := TestUtils.check_eq(first, normal, "focus skips hidden and disabled controls")
+	hidden.free()
+	disabled.free()
+	normal.free()
+	return a