Add multi-hop graph traversal API with expressive query patterns

[ravisuhag]

Context

The current lineage API supports single-direction, single-depth neighborhood lookups. Real questions require richer graph traversal across multiple hops, entity types, and relationship types.

Scope

New graph query API supporting:

• Multi-hop traversal — traverse N hops in any direction with configurable depth
• Type-filtered traversal — "follow only `produces` edges" or "stop at `dashboard` nodes"
• Path queries — "show the full data flow from this Kafka topic to this dashboard"
• Temporal filters — "what changed upstream in the last 24 hours"
• Bidirectional queries — explore both upstream and downstream in a single request

Example Queries

• "If I change this table's schema, which dashboards break?" — downstream traversal, stop at dashboard type
• "Show the full data flow from this Kafka topic to the executive dashboard" — path query
• "What changed upstream of this metric this week?" — upstream traversal with time filter

Design Considerations

• Pagination for large result sets
• Cycle detection in the graph
• Performance: index strategies for common traversal patterns
• Response format: nodes + edges with metadata, suitable for visualization and LLM consumption

Dependencies

• Typed relationship storage (Support typed relationships and rich graph ingestion from Meteor #232)

References

• Compass Roadmap — Graph-Native Store