lookup_entity codegen path can't generate DQ artefact tables

ores.codegen.lookup_entity org models (e.g. projects/ores.dq/modeling/ores.dq.report_definition_lookup_entity.org) declare a * Primary key=/=* Columns=/=* Artefact indexes shape whose archetype doc (sql_schema_artefact_create.org) claims to be "invoked directly by generator.py on the dataset path". In the current CLI (codegen.sh generate), the model's #+type: resolves to model-type 'enum', and 'enum' models dispatch to get_enum_template_mappings() — unrelated to sql_schema_artefact_create.mustache. Running codegen.sh generate --model ores.dq.report_definition_lookup_entity.org produces "nothing to generate for 'sql' (model type 'enum')". The artefact table already in the tree (dq_report_definitions_artefact_create.sql, carries an AUTO-GENERATED header) must have been produced by an older, since refactored generator — the facet is dead for the present tooling. Either wire lookup_entity models into the address/facet system (a new facet route mapping model-type 'enum' or a renamed dedicated type to sql_schema_artefact_create.mustache + sql_populate_function_refdata.mustache), or retire the lookup_entity archetype docs/templates if the pattern is no longer intended to be live.

Discovered while scoping Add librarian support for currency pairs: wanted to codegen currency_pairs's DQ artefact staging table the same way report_definitions's was (apparently) generated, and found the path non-functional. Ended up hand-writing the artefact table/populate/ publish-from-dq instead, consistent with how currencies, countries, and the synthetic FX spot config (task 44030333-A650-4EBF-9674-5819B8496114, "no codegen facet, that work is deferred") are already hand-written. If a future entity's DQ artefact pipeline is expected to be codegen-driven, this gap needs closing first.

• projects/ores.codegen/library/templates/sql_schema_artefact_create.org
• projects/ores.dq/modeling/ores.dq.report_definition_lookup_entity.org
• projects/ores.codegen/src/codegen/core.py — get_model_type, the is_enum dispatch branch, get_enum_template_mappings

• Currency pair support in reference data
• Model synthetic FX spot config as a DQ artefact type