test(e2e): address self-review follow-ups (dedup, XSS render guard, SSE hardening)

Follow-ups from the code review of the test-quality batches:

- Consolidate duplicated helpers into e2e/helpers/: seed.ts (seedUpload,
  seedComment, listComments, findFeedRow) and sse.ts (mintSseTicket, openStream,
  trackStreamOpens). Refactor authorization-deep, xss-injection, like-comment,
  sse-ticket-abuse, ddos, sse-realtime, multi-tab, and SseListener to use them —
  the upload/comment/ticket-flow contracts now live in one place each instead of
  being re-inlined across 3–7 specs.
- xss-injection display-name loop: it navigated to /feed (which renders uploader
  names, not the viewer's) so "nothing fired" passed vacuously — the payload was
  never rendered. Now navigate to /account (the actual sink) and add a render
  guard asserting the payload reached the DOM as escaped text before checking
  __xssFired.
- sse-realtime reconnect: snapshot the stream-open count AFTER backgrounding, so
  the "new connection" assertion is attributable to the foreground event and can't
  be satisfied by a spurious native/error reconnect before the toggle.
- recover-page: correct the comment (auto-submit is the onPinInput handler, not an
  $effect).

44 affected specs verified green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

e2e/specs/07-adversarial/authorization-deep.spec.ts

@@ -5,37 +5,10 @@
  * with cross-user and banned-user scenarios that span multiple resources.
  */
 import { test, expect } from '../../fixtures/test';
-import { uploadRaw, JPEG_MAGIC } from '../../helpers/upload-client';
+import { seedUpload, seedComment, listComments, findFeedRow } from '../../helpers/seed';
 
 const BASE = process.env.E2E_FRONTEND_URL ?? 'http://localhost:3101';
 
-/** Seed a real upload owned by `jwt` and return its id. */
-async function seedUpload(jwt: string, caption?: string): Promise<string> {
-  const body = new Uint8Array(1024);
-  body.set(JPEG_MAGIC, 0);
-  const res = await uploadRaw(jwt, body, { filename: 'a.jpg', contentType: 'image/jpeg', caption });
-  if (res.status !== 201) throw new Error(`seed upload failed: ${res.status} ${await res.text()}`);
-  return (await res.json()).id;
-}
-
-/** Seed a real comment on `uploadId` authored by `jwt`; return its id. */
-async function seedComment(jwt: string, uploadId: string, body = 'mine'): Promise<string> {
-  const res = await fetch(`${BASE}/api/v1/upload/${uploadId}/comments`, {
-    method: 'POST',
-    headers: { Authorization: `Bearer ${jwt}`, 'Content-Type': 'application/json' },
-    body: JSON.stringify({ body }),
-  });
-  if (res.status !== 201) throw new Error(`seed comment failed: ${res.status} ${await res.text()}`);
-  return (await res.json()).id;
-}
-
-async function listComments(jwt: string, uploadId: string): Promise<any[]> {
-  const res = await fetch(`${BASE}/api/v1/upload/${uploadId}/comments`, {
-    headers: { Authorization: `Bearer ${jwt}` },
-  });
-  return res.json();
-}
-
 test.describe('Adversarial — deep authorization', () => {
   // IDOR: user B must not be able to delete user A's REAL comment. This exercises the
   // ownership guard (`comment.user_id != auth.user_id` → 403) — the previous version fired
@@ -87,13 +60,12 @@ test.describe('Adversarial — deep authorization', () => {
   });
 
   // IDOR: user B must not be able to edit (re-caption / re-tag) user A's upload.
-  test('user B cannot edit user A\'s upload caption (403, caption unchanged)', async ({ guest, db }) => {
+  test('user B cannot edit user A\'s upload caption (403, caption unchanged)', async ({ guest }) => {
     const a = await guest('UploadOwnerA2');
     const b = await guest('AttackerB3');
 
-    const uploadId = await seedUpload(a.jwt, 'original caption');
-    // Make it visible in the feed so we can read the caption back.
-    await db.setUploadCompressionStatus(uploadId, 'done');
+    // seedUpload marks compression done, so the upload is feed-visible for the read-back.
+    const uploadId = await seedUpload(a.jwt, { caption: 'original caption' });
 
     const res = await fetch(`${BASE}/api/v1/upload/${uploadId}`, {
       method: 'PATCH',
@@ -104,9 +76,7 @@ test.describe('Adversarial — deep authorization', () => {
 
     // No state change: the caption A set is intact.
     const feedRes = await fetch(`${BASE}/api/v1/feed`, { headers: { Authorization: `Bearer ${a.jwt}` } });
-    const feed: any = await feedRes.json();
-    const list: any[] = feed.uploads ?? feed.items ?? feed;
-    const row = list.find((u: any) => u.id === uploadId);
+    const row = findFeedRow(await feedRes.json(), uploadId);
     expect(row?.caption).toBe('original caption');
   });