some renaming of variables

README.md

@@ -154,8 +154,8 @@ dancers; deleting a school also deletes its dancers, groups and shows.
 
 Shows have a name, zero to six dated dayparts (`MORNING`, `AFTERNOON`, `EVENING`),
 with unique date/type combinations. The displayed date range comes from these
-dayparts. Each show stores `preferredDayParts` (x), defaulting to two or one for
-one daypart. Ordinary groups, including PRE_EDUCATION, perform in exactly x
+dayparts. Each show stores `preferredDayParts`, defaulting to two or one for
+one daypart. Ordinary groups, including PRE_EDUCATION, perform in exactly preferredDayParts
 dayparts; preschool groups once; showcases every daypart. See
 [show-scheduling-rules.md](show-scheduling-rules.md) for the full hard constraints,
 coach exceptions, ordering and optimization rules.
@@ -178,10 +178,10 @@ status. The UI supports ordering and moving performances, and displays violation
 the same body to link an existing coach. `DELETE .../coaches/{coachId}/dancer`
 removes the identity link. The dancers screen supports maintaining these links.
 
-School JSON exports use format version **3**, including x, schedule status and
+School JSON exports use format version **3**, including preferredDayParts, schedule status and
 coach-to-dancer links. Version 2 remains importable; its schedules migrate to
-drafts with default x. Version 1 is unsupported. Legacy `appearances` fields are
-retained for file compatibility; S18 scheduling uses x and fixed type exceptions.
+drafts with default preferredDayParts. Version 1 is unsupported. Legacy `appearances` fields are
+retained for file compatibility; S18 scheduling uses preferredDayParts and fixed type exceptions.
 The REST `appearances` input is deprecated; use `preferredDayParts`.
 
 Run the HTTP integration tests with: