Function decide_left_operation 

pub fn decide_left_operation<EF, V, LF>(
    conversation: ParticipantConversation,
    commit: LeaveCommit<EF, V, LF>,
) -> AggregateOperationResult<LeaveCommit<EF, V, LF>>

Selects the aggregate Left event for one consumed leave commit.

The whole LeaveCommit — tombstone AND the claim frontiers committed in the same Leave transaction — is consumed and returned intact through the barrier, so the frontier authority can never be split from the event that records its Leave.

Errors

Returns AggregateOperationFault with AggregateOperationFaultReason::LeaveIdentityNotRetired if the commit’s identity result is not a permanent tombstone — an internal invariant super::commit_leave and super::commit_pending_leave make unreachable. The shell and commit return unchanged.