A standalone browser fixture needs parent-suite discovery isolation

A standalone browser fixture needs two checks: it must pass with its own server, and the parent suite must not discover it when that suite uses a different server. A nested Playwright configuration does not automatically create a discovery boundary. With recursive testDir discovery, explicitly exclude the separately hosted fixture in the parent configuration while retaining its dedicated command.

A missing fixture-only control can look like a UI regression but actually indicate the test ran against the wrong host. Trace the selected configuration, base URL, server and discovered file before changing product code or adding retries.

Verification method: run the dedicated fixture and check parent discovery using Playwright's matcher or --list. A matcher-only check proves exclusion patterns, not full browser execution or global setup. This lesson applies when fixtures genuinely require a different harness; application E2E tests should remain in the application suite.