Function co_declared_branch 

fn co_declared_branch(
    sources: Vec<CoDeclaredSource>,
    window: &GraphQueryWindow,
) -> Result<Option<DataFrame>>

The same-row co-declared branch: for each source table, every vocabulary pair whose two entity types the table declares yields an edge projection, expanded from one scan via unnest_rows (the registry idiom). Attribute edges carry provenance = 'attribute'; agent edges are span-structure observations and carry provenance = 'trace'.