fix(connect-groups): use selectable Rock schedule fields

[tataihono]

Summary

• stop selecting Rock's computed FriendlyScheduleText through OData
• keep the direct-response field optional in the external contract
• use the persisted schedule Description when the computed field is absent

Production evidence

The corrected 08:30 UTC worker reached Connect Groups and Rock rejected FriendlyScheduleText in $select, even though direct Schedules/{id} responses include the computed property.

Verification

• 21 focused tests across reconciliation, mapping, and cache hooks
• focused ESLint
• git diff --check