chore(client): add gdUnit4 test framework addon

Vendor gdUnit4 for Godot 4 client testing (D-030).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

client/addons/gdUnit4/src/ui/menu/GdUnitContextMenuItem.gd

@@ -0,0 +1,45 @@
+class_name GdUnitContextMenuItem
+
+
+var command_id: String:
+	set(value):
+		command_id = value
+	get:
+		return command_id
+
+var name: StringName:
+	set(value):
+		name = value
+	get:
+		return name
+
+var visible: Callable:
+	set(value):
+		visible = value
+	get:
+		return visible
+
+var icon: Texture2D:
+	get:
+		return GdUnitCommandHandler.instance().command_icon(command_id)
+
+
+func _init(p_command_id: String, p_name: StringName, p_is_visible: Callable) -> void:
+	assert(p_command_id != null and not p_command_id.is_empty(), "(%s) missing command id " % p_command_id)
+	assert(p_is_visible != null, "(%s) missing parameter 'GdUnitCommand'" % p_name)
+
+	self.command_id = p_command_id
+	self.name = p_name
+	self.visible = p_is_visible
+
+
+func shortcut() -> Shortcut:
+	return GdUnitCommandHandler.instance().command_shortcut(command_id)
+
+
+func is_visible(...args: Array) -> bool:
+	return visible.callv(args)
+
+
+func execute(...args: Array) -> void:
+	GdUnitCommandHandler.instance().command_execute(command_id, args)