Demo follow-ups: editable policy name, one-page signup, group classes in upcoming lessons, deletion cleanup

Five items from the latest demo pass:

- A policy's title can be edited from the Policies screen. Only the title
  moves; the slug is what the gates resolve policies by, so a rename can
  never detach a policy from acceptances already recorded against it.
- Signup is one page again. The studio's registration questions move from
  a second step behind "Next" onto the main form, in an "About you" panel
  above the students being added, and that panel also asks an adult
  student for their birth year (the same us_birth_year meta a child's
  uses). register.js disables and hides the whole panel for a pure
  guardian, since the questions describe a student.
- The password is re-scored on submit, not only as it is typed. zxcvbn's
  dictionary arrives after page load, so a password typed straight away
  was never scored at all and the first the student heard of it was the
  server rejecting the whole form.
- Group-class sessions appear alongside lessons wherever upcoming lessons
  are listed: the [us_scheduler] panel (students and instructors) and the
  admin student detail page. GroupClass\SessionSchedule derives them from
  Offering::sessionWindows(), the same derivation the billing scan uses.
  They carry kind = 'group_class' and no Cancel action - a session is one
  date in a term, not a booked slot.
- Deleting a user releases what the account was holding: each upcoming
  lesson is cancelled, its slot freed for rebooking, its pending payment
  voided, and active class enrolments cancelled. Past lessons and paid
  history are left alone.

Tests: composer test (851), composer lint, composer cs all pass.

Co-Authored-By: Claude Opus 5 <[email protected]>

docs/features/registration-questions.md

@@ -7,8 +7,8 @@ Questions come in two **scopes**:
   booking a specific offering; authored per offering by the studio admin or the owning
   instructor, and stored against the resulting lesson or group enrolment.
 - **Account scope** (`scope = 'account'`) — studio-wide questions every new student answers
-  **once at account signup**, as a required second step after choosing their name and
-  password. Authored by the studio admin only, and stored against the new user account.
+  **once at account signup**, on the same page as their name and password. Authored by the
+  studio admin only, and stored against the new user account.
 
 Both scopes share the `us_questions` / `us_question_answers` tables, the same field types,
 and the same authoring page (**Offerings → Questions**).
@@ -49,9 +49,9 @@ lesson, a group enrolment, or an account signup (`account` + the user ID).
 2. Required questions block submission until answered.
 3. Answers are sent in the `answers[]` array on `POST /bookings` or `POST /enrollments` and written to `us_question_answers` alongside the new registration row.
 
-## Account-scope Flow (signup step two)
+## Account-scope Flow (signup)
 1. The `[us_student_register]` page (`Auth\RegistrationPage`) loads active account-scope questions via `QuestionRepository::findByScope('account')`.
-2. The form renders as two steps: step one is email/name/password/policies, step two is the questions. `assets/js/register.js` reveals step two behind a "Next" button (progressive enhancement — without JS both steps show and the single submit still works). This applies to **every** signup path (invite, group link, self-approval).
+2. The form is a single page. The questions sit in an **About you** panel, alongside the account holder's birth year, between the "Who are you registering?" choice and the students being added. `assets/js/register.js` disables and hides that whole panel when the choice is "on behalf of students" — the questions describe a student and a pure guardian is not one — and puts the same questions in every child block instead. Progressive enhancement: without JS every panel shows and the single submit still works. This applies to **every** signup path (invite, group link, self-approval).
 3. On submit, required answers are validated **before** the user is created (a missing answer returns an error and creates no account); after creation each answered question is written to `us_question_answers` with `registration_type = 'account'`, `registration_id = student_id = <new user ID>`.
 4. A studio admin reviews the answers on the student's admin screen under **Registration Information** (`Auth\StudentHistory::registrationInfo()` lists every account question paired with the student's answer, "—" when unanswered). These rows are excluded from the offering-scope "Intake answers" table.
 
@@ -77,7 +77,7 @@ through the server-rendered admin page and read directly by `RegistrationPage`.
 - Models: `Unsupervised\Schedular\Registration\Question` (`scope`, nullable `offeringId`), `Unsupervised\Schedular\Registration\Answer` (`REG_ACCOUNT`)
 - Admin controller: `Unsupervised\Schedular\Registration\QuestionController`
 - REST endpoint: `Unsupervised\Schedular\Registration\QuestionEndpoint` (offering scope only)
-- Signup step two: `Unsupervised\Schedular\Auth\RegistrationPage`, `templates/frontend/register-page.php`, `assets/js/register.js`
+- Signup form: `Unsupervised\Schedular\Auth\RegistrationPage`, `templates/frontend/register-page.php`, `assets/js/register.js`
 - Admin review: `Unsupervised\Schedular\Auth\StudentHistory::registrationInfo()`, `templates/admin/student-detail.php`
 - Schema: `us_questions.scope` + nullable `us_questions.offering_id` (requires a plugin version bump so `dbDelta` runs)
 - Nullability repair: `dbDelta` does **not** reliably relax a column from `NOT NULL` to `NULL`, so sites created before account-scope questions kept `offering_id NOT NULL` and rejected account inserts. `QuestionRepository::ensureOfferingNullable()` re-applies the nullable definition (idempotent `ALTER … MODIFY`); `Plugin::boot()` runs it once, guarded by the `us_questions_offering_nullable` option rather than the version gate (affected sites may already be on the current version)