codeanalyzer-java: Neo4j v2 base relabel

[sinha108]

Plan (optional)

Design spec: https://github.com/codellm-devkit/codeanalyzer-java/blob/main/docs/design/specs/schema-v2-l3-l4-design.md

Problem

neo4j/SchemaCatalog is at v1 1.0.0 with old node families (JCompilationUnit, JType is_* booleans, JCallable with code) and J_CALLS carrying type/weight/source_kind/destination_kind. It must project the v2 CPG (L1/L2 layer).

Scope boundary

L1/L2 Neo4j families only — the dataflow overlays (J_CFG_NEXT/J_CDG/J_DDG/J_PARAM_*/J_SUMMARY) ride in the L3/L4 issues. Reuse the existing GraphProjector/RowBuilder/GraphRows/CypherWriter/BoltWriter machinery; keep the dual-label JSymbol merge pattern and _module provenance.

Goals

• v2 node families keyed by can:// id: JApplication, JModule, JSymbol (+ specific type-kind label), JCallable, JField, JParameter
• J_-prefixed relationships (D9): J_HAS_MODULE, J_DECLARES, J_HAS_CALLABLE, J_HAS_FIELD, J_RESOLVES_TO, J_CALLS(weight,prov), J_EXTENDS, J_IMPLEMENTS
• SchemaCatalog major version bump; --emit schema reflects the new families
• --emit neo4j runs at full implemented depth; -a/--graph-field-depth alongside --emit neo4j is an explicit non-zero error

Caveats and known risks

• Families rename = major graph-schema change; moves in lockstep with the JSON schema.
• Deferred-edge (no-dangling) discipline; unresolved-string fallback rides on the source node's props.

Definition of done

• --emit schema produces a schema.neo4j.json listing every v2 node family the JSON emits.
• --emit neo4j (no URI) writes a graph.cypher that loads clean against an empty Neo4j and is idempotent.
• Cross-projection gate: Neo4j node/edge counts at full depth match the JSON at max_level (modulo explicit HAS_* containment); no dangling relationships.