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/board.spec.js

@@ -1,45 +1,76 @@
 import { test, expect } from './helpers/fixtures.js'
+import { loginAsMember } from './helpers/auth.js'
+
+// The default `memberPage` fixture authenticates as test-admin@ghostguild.dev,
+// the same account auth.spec.js's logout test revokes mid-suite. Bypass the
+// fixture and use a seeded, non-shared member instead so cross-file logout
+// can't strand this file mid-flow.
+const SEEDED_MEMBER_EMAIL = 'riley.johnson@cooperativedev.org'
+
+const newMemberPage = async (browser) => {
+  const context = await browser.newContext()
+  const page = await context.newPage()
+  await loginAsMember(page, SEEDED_MEMBER_EMAIL)
+  return { context, page }
+}
 
 test.describe('Board page', () => {
-  test('page loads for authenticated member', async ({ memberPage }) => {
-    await memberPage.goto('/board')
-    await expect(memberPage.getByRole('heading', { name: 'Board' })).toBeVisible({ timeout: 15000 })
-    await expect(memberPage.getByRole('button', { name: '+ New Post' }).first()).toBeVisible()
-  })
-
-  test('clicking New Post reveals the form', async ({ memberPage }) => {
-    await memberPage.goto('/board')
-    await memberPage.waitForLoadState('networkidle')
-    await expect(memberPage.getByRole('button', { name: '+ New Post' }).first()).toBeVisible({
-      timeout: 15000,
-    })
-
-    await memberPage.getByRole('button', { name: '+ New Post' }).first().click()
-
-    await expect(memberPage.getByRole('heading', { name: 'New post' })).toBeVisible()
-    await expect(memberPage.locator('#post-title')).toBeVisible()
-    await expect(memberPage.locator('#post-seeking')).toBeVisible()
-  })
-
-  test('tags drawer toggles open and closed', async ({ memberPage }) => {
-    await memberPage.goto('/board')
-    await expect(memberPage.getByRole('heading', { name: 'Board' })).toBeVisible({ timeout: 15000 })
-
-    const drawerToggle = memberPage.getByRole('button', { name: /^Tags\.\.\./ })
-    // Drawer toggle only appears if cooperative tags exist — skip quietly if not
-    if (!(await drawerToggle.isVisible().catch(() => false))) {
-      test.skip(true, 'No cooperative tags seeded in this environment')
-      return
+  test('page loads for authenticated member', async ({ browser }) => {
+    const { context, page: memberPage } = await newMemberPage(browser)
+    try {
+      await memberPage.goto('/board')
+      await expect(memberPage.getByRole('heading', { name: 'Bulletin Board' })).toBeVisible({ timeout: 15000 })
+      await expect(memberPage.getByRole('button', { name: '+ New Post' }).first()).toBeVisible()
+    } finally {
+      await context.close()
     }
-
-    await drawerToggle.click()
-    await expect(memberPage.getByText('Filter:')).toBeVisible()
-
-    await drawerToggle.click()
-    await expect(memberPage.getByText('Filter:')).not.toBeVisible()
   })
 
-  test('create, edit, and delete own post', async ({ memberPage }) => {
+  test('clicking New Post reveals the form', async ({ browser }) => {
+    const { context, page: memberPage } = await newMemberPage(browser)
+    try {
+      await memberPage.goto('/board')
+      await memberPage.waitForLoadState('networkidle')
+      await expect(memberPage.getByRole('button', { name: '+ New Post' }).first()).toBeVisible({
+        timeout: 15000,
+      })
+
+      await memberPage.getByRole('button', { name: '+ New Post' }).first().click()
+
+      await expect(memberPage.getByRole('heading', { name: 'New post' })).toBeVisible()
+      await expect(memberPage.locator('#post-title')).toBeVisible()
+      await expect(memberPage.locator('#post-seeking')).toBeVisible()
+    } finally {
+      await context.close()
+    }
+  })
+
+  test('tags drawer toggles open and closed', async ({ browser }) => {
+    const { context, page: memberPage } = await newMemberPage(browser)
+    try {
+      await memberPage.goto('/board')
+      await expect(memberPage.getByRole('heading', { name: 'Bulletin Board' })).toBeVisible({ timeout: 15000 })
+
+      const drawerToggle = memberPage.getByRole('button', { name: /^Tags\.\.\./ })
+      // Drawer toggle only appears if cooperative tags exist — skip quietly if not
+      if (!(await drawerToggle.isVisible().catch(() => false))) {
+        test.skip(true, 'No cooperative tags seeded in this environment')
+        return
+      }
+
+      await drawerToggle.click()
+      await expect(memberPage.getByText('Filter:')).toBeVisible()
+
+      await drawerToggle.click()
+      await expect(memberPage.getByText('Filter:')).not.toBeVisible()
+    } finally {
+      await context.close()
+    }
+  })
+
+  test('create, edit, and delete own post', async ({ browser }) => {
+    const { context, page: memberPage } = await newMemberPage(browser)
+    try {
     await memberPage.goto('/board')
     await memberPage.waitForLoadState('networkidle')
     await expect(memberPage.getByRole('button', { name: '+ New Post' }).first()).toBeVisible({
@@ -85,5 +116,8 @@ test.describe('Board page', () => {
     await expect(memberPage.getByRole('heading', { name: editedTitle })).not.toBeVisible({
       timeout: 10000,
     })
+    } finally {
+      await context.close()
+    }
   })
 })