M4 Neo4j projection at L1 depth: rows, cypher/bolt writers, schema catalog

[rahlk]

Part of #27. neo4j/ subpackage: project() -> GraphRows -> cypher snapshot + optional bolt push; declarative schema catalog + --emit schema (schema.neo4j.json); containment as HAS_*/DECLARES, hierarchy as EXTENDS/IMPLEMENTS; kinds->labels lockstep with SCHEMA_DECISIONS.md. Gate: schema-conformance test; --emit neo4j full-depth rule enforced.