feat: neo4j EXTENDS/IMPLEMENTS inheritance edges #33

Type: feat · Branch: feat/issue-33-neo4j-inheritance-edges · Part of epic #26 · Lands last

Problem

Base classes / implemented interfaces are stored as string-array node props (src/build/neo4j/project.ts:151); REL_TYPES (src/build/neo4j/schema.ts:129-153) has no EXTENDS/IMPLEMENTS, and the spec's deferred edgeToSymbol gate (src/build/neo4j/rows.ts:88-98) is dead code. Class hierarchy is not graph-queryable, and the resolved-only structural guarantee is unwired (neo4j-projection.md:153,175).

Open sub-check (do FIRST)

Confirm against canonical-schema.md / the SDK model whether the JSON projection should also gain an inheritance edge list or keep the current base_classes props — match Java/Python (parity). Default for this issue: Neo4j edges + keep JSON props. Record the decision in .claude/SCHEMA_DECISIONS.md.

Change

1. Resolve heritage signatures → declaring-node can:// ids in the emitter where idBySig lives (src/schema/v2/emit.ts); expose extends_ids / implements_ids on the V2 type node (drop unresolved/external supertypes).
2. Add EXTENDS, IMPLEMENTS to REL_TYPES (src/build/neo4j/schema.ts); bun run gen:schema to refresh schema.neo4j.json.
3. Emit the edges in project() (src/build/neo4j/project.ts) via the now-revived edgeToSymbol deferred gate (base class → EXTENDS, interface → IMPLEMENTS). Reviving the gate closes the dead-code finding.
4. Add a first-party class-hierarchy fixture if none exists.

Acceptance

• Class hierarchy graph-queryable via EXTENDS/IMPLEMENTS; edges non-dangling; conformance gate declares both rel types; checked-in schema.neo4j.json matches gen:schema.

Files: src/schema/v2/emit.ts, src/build/neo4j/schema.ts, schema.neo4j.json, src/build/neo4j/project.ts, src/build/neo4j/rows.ts, test + fixture, .claude/SCHEMA_DECISIONS.md.