@spec isolated_participants(Choreo.Sequence.t()) :: [atom()]

Returns participants that never send or receive a message.

@spec missing_labels(Choreo.Sequence.t()) :: [{:error, String.t()}]

Returns messages that are missing labels.

@spec unbalanced_activations(Choreo.Sequence.t()) :: [{:warning, String.t()}]

Detects unbalanced activation boxes.

Returns {participant, imbalance} where imbalance is positive if there are more activates than deactivates and negative if there are more deactivates than activates.

@spec unclosed_fragments(Choreo.Sequence.t()) :: [{:error, String.t()}]

Detects fragments that were opened but never closed.

@spec unknown_participants(Choreo.Sequence.t()) :: [{:error, String.t()}]

Returns events that reference unknown participants.

@spec validate(Choreo.Sequence.t()) :: [{:error | :warning, String.t()}]

Validates the sequence diagram and returns a list of issues.

Each issue is a tuple of {severity, message} where severity is :error or :warning.