fix(client): resolve GDScript autoload parse-order errors

Autoload scripts are parsed before regular scripts, so class_name
types (CharacterVisualDescriptor, TestHarness, YamlParser) are not
available at parse time. Replace type annotations with untyped vars
and use load() for in-body class references. Fixes all 14 headless
parse errors (9 pre-existing + 5 from Sprint 30 changes).

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

client/scripts/autoloads/ui_strings.gd

@@ -51,4 +51,4 @@ func reload() -> void:
 ## Returns flat Dictionary with dotted keys: { "section.sub.key": "value" }.
 ## Delegates to YamlParser.parse_flat() (#560).
 static func _parse_yaml(text: String) -> Dictionary:
-	return YamlParser.parse_flat(text)
+	return load("res://scripts/util/yaml_parser.gd").parse_flat(text)