Generic widget names such as model_name are no longer treated as local
model references by default. Only folder-backed schemas, known widget
indexes, or a model-typed combo/output pairing now admit an extensionless
value.
This prevents metadata/search nodes (for example Civitai Hash Fetcher)
with a model_name STRING input from being incorrectly reported as missing
models.
Added test_model_name_string_used_as_metadata_query_is_ignored to cover
the regression.