Completed studies: finishing a study keeps access after leaving; certificates always shown; no reminders for finished studies; v2.11.0

- Completion is stored on the user (completedStudySlugs, sticky) when every lesson is done; backfilled at startup
- Lessons, notes, progress, quiz, community and certificate stay open for completed studies after leaving the enrollment
- Dashboard/My Account list completed studies with Review Lessons and certificate access
- Study page shows a completed banner
- Lesson-release reminders, weekly digest and re-engagement emails skip finished studies
- Fix: streak fields (current/longest/last studied) and firstCompletionAt were dropped on every restart when users were loaded
- Tests for completion/access/re-engagement

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

test/study-completion.test.js

@@ -0,0 +1,61 @@
+import { test } from 'node:test'
+import assert from 'node:assert/strict'
+import { state } from '../server/state.js'
+import {
+  hasStudyAccess,
+  isStudyUserCompleted,
+  getAccessibleStudySlugs,
+  markStudyCompletedIfDone,
+  scheduleReengagementEmails,
+} from '../server/study-helpers.js'
+
+function setup() {
+  state.cachedSiteContent = {
+    studies: [{ slug: 'mini', sections: [{ id: 'a' }, { id: 'b' }] }, { slug: 'other', sections: [{ id: 'x' }] }],
+  }
+}
+
+test('completing every lesson marks the study completed and keeps access after leaving', () => {
+  setup()
+  const user = { id: 'u1', enrolledStudySlugs: ['mini'] }
+  assert.equal(markStudyCompletedIfDone(user, 'mini', ['a']), false)
+  assert.equal(markStudyCompletedIfDone(user, 'mini', ['a', 'b']), true)
+  assert.ok(isStudyUserCompleted(user, 'mini'))
+
+  user.enrolledStudySlugs = [] // student leaves
+  assert.ok(hasStudyAccess(user, 'mini'))
+  assert.ok(!hasStudyAccess(user, 'other'))
+  assert.deepEqual(getAccessibleStudySlugs(user), ['mini'])
+})
+
+test('completion is sticky when a lesson is added later, and not marked twice', () => {
+  setup()
+  const user = { id: 'u2', enrolledStudySlugs: ['mini'] }
+  markStudyCompletedIfDone(user, 'mini', ['a', 'b'])
+  state.cachedSiteContent.studies[0].sections.push({ id: 'c' })
+  assert.equal(markStudyCompletedIfDone(user, 'mini', ['a', 'b']), false)
+  assert.ok(isStudyUserCompleted(user, 'mini'))
+  assert.deepEqual(user.completedStudySlugs, ['mini'])
+})
+
+test('unknown or empty studies are never marked completed', () => {
+  setup()
+  const user = { id: 'u3', enrolledStudySlugs: [] }
+  assert.equal(markStudyCompletedIfDone(user, 'nope', ['a']), false)
+  state.cachedSiteContent.studies.push({ slug: 'empty', sections: [] })
+  assert.equal(markStudyCompletedIfDone(user, 'empty', []), false)
+})
+
+test('re-engagement emails skip students whose only study is finished', async () => {
+  setup()
+  const sent = []
+  state.studyUsers = [{
+    id: 'u4', username: 'a@b.co', studyRemindersEnabled: true, lastLoginAt: new Date(Date.now() - 40 * 864e5).toISOString(),
+    enrolledStudySlugs: ['mini'], completedStudySlugs: ['mini'], reengagementSentAt: {},
+  }, {
+    id: 'u5', username: 'c@d.co', studyRemindersEnabled: true, lastLoginAt: new Date(Date.now() - 40 * 864e5).toISOString(),
+    enrolledStudySlugs: ['mini'], reengagementSentAt: {},
+  }]
+  await scheduleReengagementEmails(async (email) => { sent.push(email) })
+  assert.deepEqual(sent, ['c@d.co'])
+})