The hour carries an as needed (PRN) slot and nothing that is owed. Excluded from `plannedCount`, `completedCount`, `skippedCount` and `incompleteCount` — see `prnCount` and `TreatmentInfo.prnTimes`. A new enum value, so a **breaking change** for a client generated against an earlier schema. `PRN` only ever appears where `NONE` would have, never displacing `DUE`, `LATE`, `PLANNED`, `COMPLETED`, `SKIPPED` or `INACTIVE`, so an unaware client falls through to its default rendering rather than mistaking a PRN slot for owed work.