createTombstoneCheckpoint
suspend fun createTombstoneCheckpoint(agentId: String, time: Instant, parentId: Long): AgentCheckpointData(source)
Creates and saves a tombstone checkpoint for an agent's session.
A tombstone checkpoint represents a placeholder state with no interactions or messages, marking a terminated or invalid session. The method generates the tombstone checkpoint and persists it using the appropriate storage mechanism.
Return
The created tombstone checkpoint data.