Refactor game mode scoring and win conditions

* Add overridable hooks for sunk/reaped ball handling and turn behavior.
* Implement default scoring and game-over messaging across game modes.
* Add pretty game mode names for win-condition messages.
* Update Free Ball, Last Ball, and Snooker modes to return win-condition messages.
* Move the reset button lookup to the scene root for multiplayer setup.
* Move camera controller scene to shared base UI. Move parts of it to new game_data UI node.
* Add commented test state generation for end-state testing.

controllers/game/modes/snooker.gd

@@ -40,5 +40,5 @@ func on_ball_sunk(ball: Node3D) -> void:
 func score_sunk_balls() -> bool:
 	return true
 
-func process_win_condition() -> void:
-	pass
+func process_win_condition() -> String:
+	return super()