test(e2e): isolate runs and identities without a new backend endpoint (WP-74)

The three specs shared one mutable backend and said so in their own
comments ("Restart the backend between CI runs"). WP-70 recorded the fix as
a dev-only seed endpoint; it isn't needed. The DB path already routes
through IConfiguration, so playwright.config's webServer hands the backend a
throwaway SQLite file per invocation — the same trick TestWebApplicationFactory
already uses, with zero backend change. And StubIdentityProvider already
honoured X-Subject; the only gap was that nothing sent it. That matters
because the backend has no IsDevelopment() gate anywhere, so a seed endpoint
would have had to invent the codebase's first environment gate.

subjectInterceptor mirrors the existing roleInterceptor and is wired into the
same isDevMode()-only list. Interceptors alone were not enough: the raw XHR
upload and the hand-written letter-preview fetch bypass Angular's chain (as
CLAUDE.md documents), so both now stamp X-Subject explicitly — without that,
every uploaded document still landed under DemoOwner.

reuseExistingServer stays on: flipping it would break local runs for anyone
already serving the docker stack. Each run gets a unique DB filename and
global-setup sweeps only prior runs' leftovers — deleting a fixed path
mid-run risks SQLite silently recreating an empty, unmigrated file under
fullyParallel.

Verified: e2e passes twice back-to-back with no backend restart, and
X-Subject was observed on a real request, not merely wired.

brief-v2.spec.ts keeps the shared identity for now — see the KNOWN GAP note;
a backend staleness bug makes /brief/preview return a sent letter with the
draft watermark for any non-DemoOwner BSN. actors.ts reserves the actor for
whoever fixes it.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

e2e/brief-v2.spec.ts

@@ -7,10 +7,22 @@ import { Actors, loginAs } from './support/actors';
 // Preview assertions are content-type/body-level (text/html + watermark marker), not
 // pixel, per WP-28's decision.
 //
-// The backend persists to SQLite (WP-22) and is shared across runs: `/brief/reset`
-// covers the letter, but org templates have no reset endpoint, so this test restores
-// the org-template draft it edits (step 8) and never asserts an absolute version
-// number — only that it increased by exactly one.
+// This test mutates real state (a letter, keyed per-owner by `BriefStore.GetOrCreate`),
+// and WP-74 gives it a fresh throwaway backend DB every `npm run e2e` run, so a
+// leftover/in-progress letter from a PREVIOUS RUN is never an issue any more. It
+// deliberately still logs in as the shared `Actors.zorgverlener` rather than its own
+// BSN, though: giving it a distinct BSN (as `smoke.spec.ts` does) hit a real,
+// reproducible bug in this repo's own e2e run — `GET /brief/preview`'s sent-letter
+// response kept the DRAFT watermark under a non-`DemoOwner` `X-Subject`, even though
+// the outgoing request carried the right header and a direct `curl` against the same
+// backend at the same instant returned the correct, frozen archive. That points to a
+// backend-side staleness/race in `BriefStore`'s SQLite read path (see
+// `letter-preview.adapter.ts`'s "KNOWN GAP" note), out of WP-74's file scope to fix —
+// so this spec stays on the one identity that doesn't trip it, pending that backend
+// investigation. The org-template appearance is a SEPARATE, already-known gap: it's
+// NOT owner-keyed (there's exactly one, shared by every caller) and has no reset
+// endpoint, so this test still restores the org-template draft it edits (step 8) and
+// never asserts an absolute version number — only that it increased by exactly one.
 test('drafter composes → approver sends; admin republishes appearance', async ({ page }) => {
   await loginAs(page, Actors.zorgverlener);
   await expect(page).toHaveURL(/\/dashboard$/);