Standardize button labels and document UI states

Finish the button-label audit with a surface-by-surface table, clarify Quit
game vs Quit to menu, rename Apply to Apply settings, and use string-table
keys for the new labels. Extend the smoke checklist with UI copy/button checks.
Headless 250/250, docs check OK.

src/game/ui/shift_review.gd

@@ -74,7 +74,7 @@ func _init() -> void:
 	center.add_child(restart)
 
 	var quit_btn := Button.new()
-	quit_btn.text = "Quit"
+	quit_btn.text = Strings.lookup("ui.quit_game")
 	quit_btn.pressed.connect(func(): get_tree().quit())
 	quit_btn.size_flags_horizontal = Control.SIZE_SHRINK_CENTER
 	_style_review_button(timeline)