Send students to a chosen page when registration succeeds

The Student Registration block's "After email confirmation" panel becomes
"After registration": the page it selects is now where a newly registered
student continues to, and a new autoRedirect toggle sends them there
instead of showing the link.

Only the two finished states qualify (RegistrationPage::isRegistrationComplete):
an invited student who is now logged in, and a self-signup back from the
emailed confirmation link. A validation error, an expired confirmation
link, and the intermediate "check your email" step all stay on the page so
their message is read.

The invited-student success previously had no link at all; it gains a
"Continue to your account" one. That path deliberately has no
WordPress-login-screen fallback — pointing someone already signed in at the
login screen helps nobody — so continueUrl() distinguishes "no page chosen"
from "page chosen", and the redirect does nothing until one is picked.

Closes #115

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

assets/js/blocks.js

@@ -151,18 +151,25 @@
             shortcode: 'us_student_register',
             attributes: {
                 loginPageId: { type: 'number', default: 0 },
+                autoRedirect: { type: 'boolean', default: false },
                 inviteOnlyMessage: { type: 'string', default: '' },
             },
             inspector: (attributes, setAttributes) => [
                 el(
                     PanelBody,
-                    { title: __('After email confirmation', 'unsupervised-schedular'), key: 'confirmation' },
+                    { title: __('After registration', 'unsupervised-schedular'), key: 'confirmation' },
                     el(PageSelect, {
                         label: __('Sign-in page', 'unsupervised-schedular'),
-                        help: __('Where the sign-in link shown after a student confirms their email address sends them.', 'unsupervised-schedular'),
+                        help: __('Where students are sent once registration finishes — after they confirm their email address, or straight away for an invited student.', 'unsupervised-schedular'),
                         defaultLabel: __('WordPress login screen', 'unsupervised-schedular'),
                         value: attributes.loginPageId,
                         onChange: (loginPageId) => setAttributes({ loginPageId }),
+                    }),
+                    el(ToggleControl, {
+                        label: __('Redirect automatically', 'unsupervised-schedular'),
+                        help: __('Send students straight to that page instead of showing the link. Requires a page to be chosen; errors and the "check your email" step are never skipped.', 'unsupervised-schedular'),
+                        checked: !!attributes.autoRedirect,
+                        onChange: (autoRedirect) => setAttributes({ autoRedirect }),
                     })
                 ),
                 el(