Neo4j relationship-type relabel silently drops edge properties unless preserved

Neo4j has no in-place "rename relationship type". When migrating an edge from type OLD to NEW, the common pattern MATCH (a)-[r:OLD]->(b) MERGE (a)-[:NEW]->(b) DELETE r (or CREATE (a)-[:NEW]->(b)) creates a BARE new relationship and silently DROPS all of the old edge's properties — weights, counts, timestamps, etc. The loss is invisible at migration time and only surfaces later when ranking/scoring that depends on those edge properties quietly degrades.