Raises a Spark.Error.DslError at compile verification when an edge
entity's label or a properties key is not a valid AGE identifier
(build-blocking under --warnings-as-errors — Spark emits verifier errors
as compiler diagnostics).
Edge labels are interpolated directly into Cypher (MATCH (n)-[r:LABEL]->()).
Edge property keys have no query-generation consumer yet, but a later task
will interpolate them the same way set_clauses handles vertex property
keys (SET e.<key> = $<key>), so they are validated here at declaration time
rather than deferred to when that path lands.