feat: live class sessions, CE workflow, and docs (#683)

Adds live-class session scheduling on lessons (join link, date/time,
timezone) with automatic 24h and 1h reminder emails plus a calendar
invite (.ics), a time-change notification with an updated invite, a
teacher-authored welcome email and session invite on enrollment, and a
"Notify students" quiz nudge.

LMS gets an upcoming live-sessions card and Join buttons, plus a
reusable live-session card component (3 states) in @cio/ui with a
Storybook story. The sidebar content tree now reflects sequential
progression locking like the content list, and the course-completion
confetti regression is fixed.

Org-based emails no longer reference ClassroomIO by name. Docs add
live-class, welcome-email, and course-progression guides, expand the
certificates guide (design, signatures, corrected labels), move
plan-required callouts to the top, flatten how-to-guides to the docs
root with redirects, and add screenshots. Includes an add-docs-image
skill.

packages/email/src/utils/constants.ts

@@ -7,6 +7,11 @@ export const EMAIL_IDS = [
   'newsfeedPost',
   'onPasswordReset',
   'programGoalReminder',
+  'quizAssigned',
+  'sessionReminder',
+  'sessionUpdated',
+  'submissionGraded',
+  'submissionReceived',
   'studentCourseInvite',
   'studentCourseCompletion',
   'studentCourseWelcome',

packages/email/src/utils/services/nodemailer.ts

@@ -38,7 +38,7 @@ const setupTransporter = async () => {
 };
 
 export async function sendWithNodemailer(emailData: TEmailData): Promise<EmailResponse> {
-  const { from, to, subject, content, replyTo } = emailData;
+  const { from, to, subject, content, replyTo, ics } = emailData;
 
   if (!transporter) {
     transporter = await setupTransporter();
@@ -57,7 +57,8 @@ export async function sendWithNodemailer(emailData: TEmailData): Promise<EmailRe
       to,
       subject,
       replyTo,
-      html: content
+      html: content,
+      ...(ics ? { icalEvent: { filename: 'session.ics', method: 'PUBLISH', content: ics } } : {})
     });
 
     return {

packages/email/src/utils/services/zeptomail.ts

@@ -10,7 +10,7 @@ export const zohoClient = new SendMailClient({
 });
 
 export async function sendWithZoho(emailData: TEmailData): Promise<EmailResponse> {
-  const { from, to, subject, content, replyTo } = emailData;
+  const { from, to, subject, content, replyTo, ics } = emailData;
 
   const fromData = extractNameAndEmail(from || '');
 
@@ -36,7 +36,18 @@ export async function sendWithZoho(emailData: TEmailData): Promise<EmailResponse
       ],
       subject,
       htmlbody: content,
-      reply_to: getReplyTo(replyTo)
+      reply_to: getReplyTo(replyTo),
+      ...(ics
+        ? {
+            attachments: [
+              {
+                content: Buffer.from(ics).toString('base64'),
+                mime_type: 'text/calendar',
+                name: 'session.ics'
+              }
+            ]
+          }
+        : {})
     });
 
     return {