Grant studio-admin capabilities to WordPress administrators

WordPress administrators (manage_options) now implicitly hold every
studio-admin capability via a user_has_cap filter, so the site owner runs
the studio without being assigned the separate us_studio_admin role. The
grant persists nothing and is removed on deactivation. The us_studio_admin
role still exists for non-administrator staff and does NOT confer any core
WordPress admin powers.

Also re-gate the studio-wide "Scheduler" dashboard off manage_options onto
a new view_all_lessons capability (added to the studio-admin cap set), so a
us_studio_admin user can see it too — previously it was administrator-only.

- RoleManager: STUDIO_ADMIN_CAPS constant, CAP_VIEW_ALL_LESSONS,
  grantStudioCapsToAdministrators() user_has_cap filter
- AdminMenu + LessonController: Scheduler gated on view_all_lessons
- Docs: user-roles.md cap matrix + administrator note; lesson-booking.md
- Tests: administrators receive studio caps; non-admins do not

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/features/lesson-booking.md

@@ -53,7 +53,7 @@ Group classes follow the same registration flow but enrol against an offering of
 kind `group_class`; see `group-classes.md`.
 
 ## Admin Interface
-- **Scheduler** (`manage_options` only): all upcoming lessons across all instructors
+- **Scheduler** (`view_all_lessons` — studio admin / administrators): all upcoming lessons across all instructors
 - **My Lessons** (`view_own_lessons`): upcoming lessons for the logged-in instructor
 
 ## Frontend Shortcodes

docs/features/user-roles.md

@@ -10,9 +10,17 @@ Runs the studio. Logs in via standard wp-admin. Can:
 - Create instructor accounts and set/revoke each instructor's capabilities
 - Manage offerings, intake questions, and policies
 - Configure Stripe credentials and per-student billing overrides (card / e-transfer / comp)
+- View the studio-wide scheduler (all upcoming lessons across instructors)
 - View the all-instructor payments report and export it
 
-**Capabilities:** `read`, `manage_instructors`, `manage_offerings`, `manage_questions`, `manage_policies`, `manage_billing`, `view_all_payments`, `export_payments`
+**Capabilities:** `read`, `manage_instructors`, `manage_offerings`, `manage_questions`, `manage_policies`, `manage_billing`, `view_all_lessons`, `view_all_payments`, `export_payments`
+
+> Any WordPress **administrator** (`manage_options`) implicitly holds every
+> studio-admin capability above, so the site owner runs the studio without being
+> assigned the `us_studio_admin` role. This is applied dynamically via the
+> `user_has_cap` filter (`RoleManager::grantStudioCapsToAdministrators()`) — it
+> persists nothing and is removed when the plugin is deactivated. The
+> `us_studio_admin` role exists for non-administrator staff who manage the studio.
 
 ### Instructor (`us_instructor`)
 Created by the studio admin. Logs in via standard wp-admin. Can:
@@ -41,6 +49,7 @@ Logs in via the front-end `[us_student_login]` shortcode. Can:
 | `manage_policies`     | ✓            |            |         | Policies                        |
 | `manage_billing`      | ✓            |            |         | Payments (Stripe + overrides)   |
 | `book_lesson`         |              |            | ✓       | Lesson booking / enrolment      |
+| `view_all_lessons`    | ✓            |            |         | Scheduler dashboard             |
 | `view_own_lessons`    |              | ✓          | ✓       | Lesson + group views            |
 | `view_own_payments`   |              | ✓          |         | Payment reporting               |
 | `view_all_payments`   | ✓            |            |         | Payment reporting               |