feat(game): refactor ball state and turn handling

* Replace `valid_end` with `is_foul` for invalid ball sinks
* Rename and centralize ball state tracking
* Add ball finalization and win-condition hooks
* Update turn switching to retain the player after valid sinks
* Apply negative points to reaped balls
* Add active-player indicator to the camera UI
* Emit active-player updates when the turn changes

controllers/game/modes/free_ball.gd

@@ -13,18 +13,29 @@ func process_ball(ball: Node3D) -> void:
 func handle_switch_user() -> void:
 	push_warning("Balls reaped: ", balls_reaped.size() )
 	push_warning("Balls sunk: ",   balls_sunk.size()   )
+	var switch_player: bool = true
 
 	if not balls_reaped.is_empty():
-		# TODO: Handle points, etc
+		for ball_name in balls_reaped:
+			ball_states[ball_name]["points"] = -ball_states[ball_name]["points"]
+
 		balls_reaped.clear()
 
-	if balls_sunk.is_empty():
-		Globals.game_state.switch_active_player()
-		turn_count += 1
+	if not balls_sunk.is_empty():
+		# TODO: Handle points, etc
+
+		switch_player = false
+		balls_sunk.clear()
+
+	if ball_states_finalized():
+		process_win_condition()
 		return
 
-	# TODO: Handle points, etc
-	# Globals.multiplayer_data.current_turn_player_id
+	if switch_player:
+		Globals.game_state.switch_active_player()
+		turn_count += 1
+	else:
+		turn_count += 1
 
-	balls_sunk.clear()
-	turn_count += 1
+func process_win_condition() -> void:
+	pass