Add group-class scheduling, instructor assignment, and details/invite management

Group classes now carry a specific class time (alongside date and duration)
and an assigned instructor:

- Schema: add `class_time` (TIME) to `us_offerings`; `Offering` gains
  `normalizeTime`/`sessionWindows`. (Rides the pending 1.0.0->1.1.0 dbDelta
  upgrade, so no version bump.)
- Offering form: class-time field, plus a studio-admin instructor picker
  (plain instructors always own their own classes).
- `ClassSlotReconciler`: assigning an instructor clears their open booking
  slots overlapping each session and flags already-booked lessons that clash
  (a booked lesson is never deleted). Uses new
  `AvailabilityRepository::findOverlapping`.
- Front end: `GET /offerings` exposes `instructor_name`; the enrolment page
  shows who teaches each class and when it meets.

Back-office group-class views redesigned:

- Instructor **My Group Classes** and studio-admin **Group Classes** are now
  per-class summaries with enrolment counts, not flat student lists.
- Each links through (`?class_id=<id>`) to a per-class **details page**
  (schedule panel, roster with payment status, and — for invite-only classes
  — the add/make-available/invite-by-email controls). Invite-only membership
  is managed entirely from this page.
- Invite actions are allowed for the class's owning instructor or any
  `view_all_lessons` studio admin, so an owner-operator (studio admin who also
  teaches) can reach every class's roster and invites from the Group Classes
  page.

Tests: composer test (508), composer lint, composer cs all pass.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

docs/features/group-classes.md

@@ -17,11 +17,17 @@ A group class can be marked **invite-only** (`us_offerings.access_mode = invite_
 | `payment_id`   | BIGINT UNSIGNED  | Nullable FK → `us_payments.id`                             |
 | `enrolled_at`  | DATETIME         | Insertion time                                             |
 
-## Class Dates
-A group class offering carries `term_start`/`term_end` (see `offerings.md`):
-one-off classes end the day they start; weekly classes run a set number of
-sessions. The class card on the enrolment page shows the date or date range
-with the session count.
+## Class Dates, Time, and Instructor
+A group class offering carries `term_start`/`term_end` plus a `class_time` and an
+owning `instructor_id` (see `offerings.md`): one-off classes end the day they
+start; weekly classes run a set number of sessions, all at `class_time`. The class
+card on the enrolment page shows **when** the class meets (the date or date range
+plus the start time) and **who** teaches it (the assigned instructor's display
+name, surfaced as `instructor_name` on the `GET /offerings` response).
+
+Assigning an instructor to a scheduled class removes that instructor's open
+booking slots at the class time and flags any already-booked lesson that clashes;
+see **Instructor assignment** in `offerings.md`.
 
 ## Enrolment Flow
 The class list is loaded together with the student's own enrolments
@@ -100,19 +106,32 @@ class becomes enrollable for them — they choose whether to enrol.
 | `created_at`  | DATETIME        | Insertion time                                                       |
 
 ## Admin Interface
-- **Group Classes** (`view_all_lessons` / studio admin): all active enrolments across instructors
-- **My Lessons → My Group Classes** (`view_own_lessons` / instructor): the instructor's
-  own group classes, each showing its active-enrolment count against capacity and a
-  per-class roster of enrolled students with enrolment and payment status. Invite-only
-  classes additionally list who has been invited but not yet enrolled and carry the
-  add/make-available/invite-by-email controls (nonce-checked `usc_action` POSTs, scoped to
-  the owning instructor)
+- **Group Classes** (`view_all_lessons` / studio admin): a per-class summary across
+  instructors — each class with its instructor, when it meets, and its active-enrolment
+  count against capacity (not a flat list of individual student enrolments). Selecting a
+  class (`?class_id=<id>`) opens the same per-class **details page** described below, so a
+  studio admin — including an owner-operator who also teaches, for whom the instructor
+  **My Group Classes** menu is hidden — can view any class's roster and manage invite-only
+  membership from here. Invite actions are permitted for the class's own instructor or any
+  `view_all_lessons` studio admin.
+- **My Lessons → My Group Classes** (`view_own_lessons` / instructor): a summary of the
+  instructor's own group classes — each with when it meets and its active-enrolment count
+  against capacity, plus a **View details** link (**View & invite** for invite-only
+  classes). Selecting a class (`?class_id=<id>`, scoped to the owning instructor) opens its
+  **details page**: a class-details panel (when, instructor, enrolled/capacity, duration,
+  price, schedule note, description, status), the roster of enrolled students with enrolment
+  and payment status, and — for invite-only classes — an **Invite & enrol students** section
+  listing who has been invited but not yet enrolled alongside the add/make-available/
+  invite-by-email controls (nonce-checked `usc_action` POSTs, scoped to the owning
+  instructor). Managing who is in an invite-only class is therefore done entirely from this
+  page. The summary (`templates/admin/my-group-classes.php`) and the details page
+  (`templates/admin/my-group-class-detail.php`) are separate templates.
 
 ## Implementation
 - Repository: `Unsupervised\Schedular\GroupClass\EnrollmentRepository` (`countActiveForOffering`/`hasActiveEnrollment` enforce capacity and prevent duplicates)
 - Access grants: `Unsupervised\Schedular\GroupClass\GroupAccess` + `GroupAccessRepository` (`hasGrant`, `findGrantedOfferingIds`, `markEnrolled`, `linkStudentByEmail`)
 - Model: `Unsupervised\Schedular\GroupClass\Enrollment`
-- Admin controller: `Unsupervised\Schedular\GroupClass\GroupClassController` — `renderPage` (studio admin, `view_all_lessons`) and `renderInstructorPage` (instructor, `view_own_lessons`)
+- Admin controller: `Unsupervised\Schedular\GroupClass\GroupClassController` — `renderPage` (studio admin per-class summary, `view_all_lessons`) and `renderInstructorPage` (instructor summary + `?class_id` roster detail, `view_own_lessons`)
 - REST endpoint: `Unsupervised\Schedular\GroupClass\EnrollmentEndpoint`
 - Frontend: `Unsupervised\Schedular\GroupClass\GroupClassPage` (`[us_group_classes]` shortcode; `offering="…"` restricts it to a single class for embedding on a dedicated page — the block equivalent is the `offeringId` attribute)
 - Reuses `Registration\RegistrationGate` (intake answers + booking-scoped policy acceptance, type `enrollment`)