test(ios): committed ASWebAuthenticationSession fixture + CI lane

Follow-up to #2438 / #2448.

**Purpose.** #2448 shipped in-place capture/drive of `com.apple.SafariViewService` sign-in sheets, live-validated with a throwaway probe app. Give it a committed fixture and CI coverage on the real path.

**Required behavior.**
- Add an `expo-web-browser` `openAuthSessionAsync` (or `AppAuth`) flow to `examples/test-app` that opens a web sign-in sheet against a local/bundled IdP page (email + password + submit → callback scheme).
- Add an iOS smoke or Maestro replay lane that drives it semantically: `wait label="LOGIN"` → `press role=textfield` + `type` → `fill role=securetextfield` → `press role=button label="LOGIN"` → assert return to app.

**Observable completion.** The lane runs in CI on the shipped runner and fails if the sheet is not served (regression guard for the route bypass + runner serve).

**Dependencies.** Builds on #2448 (registry, runner serve, route probe already landed).