Function trace_v2_attribute 

pub fn trace_v2_attribute<'a>(
    schema: &Schema,
    data_model: Option<&str>,
    column: &'a str,
) -> Option<(&'a str, &'a str)>

Resolves a Trace V2 entity reference to a JSON2 root and a literal attribute key. Everything after the first dot belongs to the key, matching Trace V1’s flattened column names. Existing physical columns take precedence.