Extract shared YamlParser utility (client/scripts/util/yaml_parser.gd)
with parse() for nested typed dicts and parse_flat() for dotted-key
string format. UIStrings._parse_yaml() and ChecklistEvaluator's inline
parser both delegate to YamlParser, removing ~140 lines of duplication.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>