Add cycle detection on transitive relationship types

[anormang1992]

Summary

• Adds cycle detection to save_primitive() that prevents edges on transitive relation types (REQUIRES, DEPENDS_ON, CONSTRAINED_BY) from forming cycles, which would cause unbounded traversal in resolve_subgraph
• Learning engine catches CyclicRelationshipError and returns SKIPPED so the learning loop continues to the next gap
• Centralizes the transitive type set as TRANSITIVE_RELATION_TYPES in models.py, replacing the private _TRANSITIVE_RELS string list in graph.py
• Removes dead target refetch in _persist_reachability

Closes #33

Test plan

• 194 tests pass, zero regressions
• 9 new tests covering: self-referential edges, direct cycles (A→B→A), indirect cycles (A→B→C→A), mixed transitive types, non-transitive cycles allowed (APPLIES_TO, INCLUDES), valid transitive edges accepted
• StubRepository BFS cycle detection mirrors Neo4j Cypher behavior
• Manual verification against live Neo4j instance (Cypher reachability query)

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Adds cycle prevention for transitive relationship edges so resolve_subgraph’s unbounded traversal can’t be corrupted by cycles, and updates the learning loop to skip candidates that would introduce such cycles.

Changes:

• Introduces TRANSITIVE_RELATION_TYPES and CyclicRelationshipError in core.models, exporting them via package __init__ modules.
• Adds transitive-cycle detection to Neo4j PrimitiveRepository.save_primitive() and updates the learning engine to treat cycle attempts as SKIPPED.
• Adds/updates learning tests and enhances the test StubRepository with BFS-based cycle checks.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/vre/test_learning.py	Adds cycle-detection tests and implements matching cycle checks in the in-memory test repository.
src/vre/learning/engine.py	Catches CyclicRelationshipError during reachability persistence and returns SKIPPED; removes dead target refetch.
src/vre/core/models.py	Centralizes transitive relation types and defines a dedicated cycle error type.
src/vre/core/graph.py	Adds Neo4j-side cycle detection in save_primitive() using a reachability query; derives transitive type list from the centralized set.
src/vre/core/init.py	Re-exports CyclicRelationshipError and TRANSITIVE_RELATION_TYPES.
src/vre/init.py	Exposes CyclicRelationshipError at the top-level public API and updates parameter docs.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.