test(e2e): restore full-suite isolation and coverage

[DavidBabinec]

What changed

• add a dedicated account persona and make clean-install dashboard preflight explicit
• isolate persona-owned AI credentials, account state, content templates, and save/navigation synchronization
• update editor selectors and fixtures to current product behavior
• keep local Playwright traces and videos opt-in so long-lived streams cannot exhaust the host disk
• refresh the E2E protocol, feature matrix, and validation evidence

Why

The complete browser suite had order-dependent state leaks and stale selectors that hid real coverage gaps. These changes make the release gate deterministic while preserving disposable local data.

Verification

• bun run lint
• bunx tsc -b --pretty false
• VITE_ALLOWED_ORIGIN=http://127.0.0.1:5208 E2E_ADMIN_BASE_URL=http://127.0.0.1:5208 E2E_PUBLIC_BASE_URL=http://127.0.0.1:3034 E2E_VITE_PORT=5208 E2E_CMS_PORT=3034 bun run test:e2e (159 passed)