Function reconcile_agents 

pub fn reconcile_agents(
    existing: &SchemaRegistry,
    updated: &mut SchemaRegistry,
    unit_tables: &HashMap<String, UnitTable>,
    unit_uses: &HashMap<String, Vec<String>>,
    errors: &mut Vec<CompileError>,
) -> HashMap<String, AgentVersions>

Reconcile every agent class across every unit against existing, writing each class’s entry into updated (the document reconcile already rebuilt for events). Diagnostics go onto errors; a refused change keeps the class’s stored entry untouched, as a refused event change does.

Returns each live class’s AgentVersions, keyed <unit>.<Agent>, read from the reconciled entry — so a read-only check/test reports the version the next build will record.