The patient's own attendance window: the per-patient episode_session_* pair when complete, else
the group's session_* pair when complete. Halves are never mixed — an episode start with a
group end would measure an interval that never happened. With no complete pair the session keeps
its dating instant so it can still be placed on a day, and contributes no duration.
The patient's own attendance window: the per-patient
episode_session_*pair when complete, else the group'ssession_*pair when complete. Halves are never mixed — an episode start with a group end would measure an interval that never happened. With no complete pair the session keeps its dating instant so it can still be placed on a day, and contributes no duration.