docs: update plugin guides for _resolve_operation helper #58
Description
The FeatureChainParserMixin now includes a _resolve_operation() helper that simplifies the common dual-path pattern (string-based parsing vs config-based options fallback) used by many feature groups.
The plugin development guides in docs/guides/ should be updated to recommend _resolve_operation() for extracting operation types instead of manually calling FeatureChainParser.parse_feature_name() and falling back to options.
See mloda-ai/mloda#242 for the implementation.