The Group Classes block can be pinned to a single class via its Class
option so it can be embedded on a page dedicated to that class. On such a
page the surrounding copy already describes the class, so the card
repeated it. In single-class mode the description is now left out and the
card shows only the schedule, instructor, schedule note, price, enrolment
deadline and the enrol/withdraw controls.
The editor preview follows the same rule: BlockPreview::groupClasses()
takes the mode from the block's offeringId attribute, drops the sample
description when a class is pinned, and notes what the published page
shows. Its sample card also gained the .us-class-when and
.us-enrol-deadline elements the live markup has always rendered.
Closes#114
Co-Authored-By: Claude Opus 5 <[email protected]>