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.

scenes/ui_controls/base_ui.gd

@@ -0,0 +1,25 @@
+extends Control
+
+
+@onready var panel: Panel                   = $panel
+@onready var win_message_lbl: RichTextLabel = $panel/win_message_lbl
+
+
+func _ready() -> void:
+	setup_signals()
+	setup_multiplayer()
+
+func setup_signals() -> void:
+	MessageBus.subscribe("declare_win_condition", _on_declare_win_condition)
+
+func setup_multiplayer() -> void:
+	if not Globals.multiplayer_data.is_multiplayer_active: return
+
+
+func _on_declare_win_condition(message: String) -> void:
+	panel.visible        = true
+	win_message_lbl.text = message
+
+	await get_tree().create_timer(5).timeout
+
+	MessageBus.emit_local("game_peer_disconnected", null)