Function append_terminal_trial 

pub fn append_terminal_trial(
    storage: &dyn Storage,
    study: StudyId,
    trial: &FrozenTrial,
    clock: &dyn Clock,
) -> Result<()>

Appends one finished trial as new history in study.

The trial’s source id, number, study, and timestamps are ignored: the destination assigns a new trial id and number, and the claim heartbeat is read from clock. Its parameters (each with its distribution), canonical constraint vector, user attributes, intermediates, and terminal outcome are written in that order through the owned lifecycle calls while the study’s finalization ownership is held. Only Complete, Pruned, and Failed trials are terminal history.

Callers validate the trial against the study (objective arity, parameter compatibility, attribute keys) before calling; this function only refuses records it cannot write.

Finalization ownership is always released, including after a failure. A failure after the claim but before the terminal commit leaves the new trial Failed with an "add_trial aborted: …" reason; a trial whose terminal commit already succeeded is never overwritten.

Errors

• Error::Unsupported when storage has no trial lifecycle capability.
• Error::Conflict when a parameter has no distribution, a complete trial has no values, the trial is not terminal, the constraint vector is longer than u32::MAX, or the unbounded reservation reports exhaustion.
• Error::LostRace when the claim failed and its reservation was already gone.
• Error::Storage naming both errors when the operation and its cleanup (abandon, failed terminal, or finalization release) both failed.
• Any error from the backend’s lifecycle calls.