test(e2e): expand coverage and harden cross-file isolation

New specs (4):
- accept-invite: pre-registrant flow happy path + cadence/preset UX
- admin-pre-registrants: list, filter, action gating, redirect
- admin-series: list, create, edit (delete skipped — button no-ops)
- admin-site-content: list whitelist, edit + roundtrip on /

Extended specs (6):
- join-flow: cadence ×12 math, guidance label, paid-tier success
- events: series-pass-required, member-savings gating
- admin-events: full CRUD via /admin/events/create?edit=<id>
- admin-members: add-member submit, status select, detail nav
- a11y: add /accept-invite, /member/account, /board, /admin/pre-registrants
- wave-slack-onboarding: 9 of 16 scaffold tests now passing

Cross-file isolation hardening:
- admin-events CRUD: refresh auth cookie (auth.spec.js logout test
  bumps tokenVersion on the shared admin), wait for hydration
  before form fill, search by unique title to dodge pagination.
- board: switch memberPage from shared admin to dedicated seeded
  member to avoid the same tokenVersion race.
- wave-slack §6.4: create dedicated test member, filter by email
  before clicking, removing the "first row" anchor.

Also fixed board heading drift ("Board" → "Bulletin Board").

e2e/admin-pre-registrants.spec.js

@@ -0,0 +1,111 @@
+import { test, expect } from './helpers/fixtures.js'
+
+test.describe('Admin pre-registrants page', () => {
+  test('page loads for admin', async ({ adminPage }) => {
+    await adminPage.goto('/admin/pre-registrants')
+
+    await expect(adminPage.getByRole('heading', { name: 'Pre-Registrants' })).toBeVisible({
+      timeout: 15000,
+    })
+
+    await expect(
+      adminPage.locator('table').or(adminPage.getByText('No pre-registrants found matching your criteria')),
+    ).toBeVisible({ timeout: 15000 })
+  })
+
+  test('header action buttons render', async ({ adminPage }) => {
+    await adminPage.goto('/admin/pre-registrants')
+    await expect(adminPage.getByRole('heading', { name: 'Pre-Registrants' })).toBeVisible({
+      timeout: 15000,
+    })
+
+    await expect(adminPage.getByRole('button', { name: /^Mark as Selected/ })).toBeVisible()
+    await expect(adminPage.getByRole('button', { name: /^Send Invites/ })).toBeVisible()
+  })
+
+  test('search input filters list without crashing', async ({ adminPage }) => {
+    await adminPage.goto('/admin/pre-registrants')
+    await adminPage.waitForLoadState('networkidle')
+
+    const search = adminPage.getByPlaceholder('Search by name, email, city, role...')
+    await expect(search).toBeVisible({ timeout: 15000 })
+
+    await search.fill(`nonexistent-prereg-${Date.now()}`)
+
+    await expect(
+      adminPage.getByText('No pre-registrants found matching your criteria'),
+    ).toBeVisible({ timeout: 10000 })
+  })
+
+  test('status filter changes selection', async ({ adminPage }) => {
+    await adminPage.goto('/admin/pre-registrants')
+    await adminPage.waitForLoadState('networkidle')
+
+    const statusFilter = adminPage.getByLabel('Filter by status')
+    await expect(statusFilter).toBeVisible({ timeout: 15000 })
+
+    await statusFilter.selectOption('expired')
+    await expect(statusFilter).toHaveValue('expired')
+
+    await expect(
+      adminPage.locator('table').or(adminPage.getByText('No pre-registrants found matching your criteria')),
+    ).toBeVisible({ timeout: 10000 })
+
+    await statusFilter.selectOption('')
+    await expect(statusFilter).toHaveValue('')
+  })
+
+  test('Send Invites button is disabled with no selection', async ({ adminPage }) => {
+    await adminPage.goto('/admin/pre-registrants')
+    await expect(adminPage.getByRole('heading', { name: 'Pre-Registrants' })).toBeVisible({
+      timeout: 15000,
+    })
+
+    await expect(adminPage.getByRole('button', { name: 'Send Invites (0)' })).toBeDisabled()
+    await expect(adminPage.getByRole('button', { name: 'Mark as Selected (0)' })).toBeDisabled()
+  })
+
+  test('send invite action', async ({ adminPage }) => {
+    await adminPage.goto('/admin/pre-registrants')
+    await adminPage.waitForLoadState('networkidle')
+    await expect(adminPage.getByRole('heading', { name: 'Pre-Registrants' })).toBeVisible({
+      timeout: 15000,
+    })
+
+    // Filter to invitable statuses; pick the first row if available.
+    const statusFilter = adminPage.getByLabel('Filter by status')
+    await statusFilter.selectOption('pending')
+    await adminPage.waitForLoadState('networkidle')
+
+    const firstRow = adminPage.locator('tbody tr').first()
+    if (await firstRow.count() === 0) {
+      test.skip(true, 'No pending pre-registrants in dev DB to invite')
+      return
+    }
+
+    await firstRow.locator('.col-name').click()
+    const sendButton = adminPage.getByRole('button', { name: /^Send Invites \(\d+\)/ })
+    await expect(sendButton).toBeEnabled()
+    await sendButton.click()
+
+    await expect(adminPage.getByRole('heading', { name: 'Send Invitation Emails' })).toBeVisible()
+
+    const submitButton = adminPage.getByRole('button', { name: /^Send \d+ invitation/ })
+    await submitButton.click()
+
+    // ALLOW_DEV_TEST_ENDPOINTS=true short-circuits the Resend call; result still reports sent.
+    await expect(adminPage.getByText(/^\d+ sent$/)).toBeVisible({ timeout: 15000 })
+  })
+
+  test('non-admin redirect', async ({ browser }) => {
+    const context = await browser.newContext()
+    const page = await context.newPage()
+
+    await page.goto('/admin/pre-registrants')
+
+    await page.waitForURL((url) => !url.pathname.startsWith('/admin'))
+    expect(page.url()).not.toContain('/admin/pre-registrants')
+
+    await context.close()
+  })
+})