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/core/GdUnitResult.gd

@@ -0,0 +1,109 @@
+class_name GdUnitResult
+extends RefCounted
+
+enum {
+	SUCCESS,
+	WARN,
+	ERROR,
+	EMPTY
+}
+
+var _state: int
+var _warn_message := ""
+var _error_message := ""
+var _value :Variant = null
+
+
+static func empty() -> GdUnitResult:
+	var result := GdUnitResult.new()
+	result._state = EMPTY
+	return result
+
+
+static func success(p_value: Variant = "") -> GdUnitResult:
+	assert(p_value != null, "The value must not be NULL")
+	var result := GdUnitResult.new()
+	result._value = p_value
+	result._state = SUCCESS
+	return result
+
+
+static func warn(p_warn_message: String, p_value: Variant = null) -> GdUnitResult:
+	assert(not p_warn_message.is_empty()) #,"The message must not be empty")
+	var result := GdUnitResult.new()
+	result._value = p_value
+	result._warn_message = p_warn_message
+	result._state = WARN
+	return result
+
+
+static func error(p_error_message: String) -> GdUnitResult:
+	assert(not p_error_message.is_empty(), "The message must not be empty")
+	var result := GdUnitResult.new()
+	result._value = null
+	result._error_message = p_error_message
+	result._state = ERROR
+	return result
+
+
+func is_success() -> bool:
+	return _state == SUCCESS
+
+
+func is_warn() -> bool:
+	return _state == WARN
+
+
+func is_error() -> bool:
+	return _state == ERROR
+
+
+func is_empty() -> bool:
+	return _state == EMPTY
+
+
+func value() -> Variant:
+	return _value
+
+
+func value_as_string() -> String:
+	return _value
+
+
+func or_else(p_value: Variant) -> Variant:
+	if not is_success():
+		return p_value
+	return value()
+
+
+func error_message() -> String:
+	return _error_message
+
+
+func warn_message() -> String:
+	return _warn_message
+
+
+func _to_string() -> String:
+	return str(GdUnitResult.serialize(self))
+
+
+static func serialize(result: GdUnitResult) -> Dictionary:
+	if result == null:
+		push_error("Can't serialize a Null object from type GdUnitResult")
+	return {
+		"state" : result._state,
+		"value" : var_to_str(result._value),
+		"warn_msg" : result._warn_message,
+		"err_msg" : result._error_message
+	}
+
+
+static func deserialize(config: Dictionary) -> GdUnitResult:
+	var result := GdUnitResult.new()
+	var cfg_value: String = config.get("value", "")
+	result._value = str_to_var(cfg_value)
+	result._warn_message = config.get("warn_msg", null)
+	result._error_message = config.get("err_msg", null)
+	result._state = config.get("state")
+	return result