A content classifier for the concept facet (what the column measures),
independent of how it is stored or its measurement level. Uses name+value
agreement like data_check_demographic(), which it wraps for the demographic
concepts. Rules-only and deterministic; concepts under cryptic names are left
NA for the LLM tier in data_check to fill.
Value
one of "reaction_time", "accuracy", "condition", "age",
"gender", "race", "timestamp", or NA_character_. (id, date and
likert concepts are assigned by data_col_facets() from the role /
representation / measurement level, not here.)
