Boots the real webapp plus Postgres, Redis and s2-lite, creates a Session
through the public API so the run comes from the real trigger path, appends to
a run-scoped stream the way `streams.append()` does, and asserts the version
stamped on the run alongside where the bytes actually landed.
The harness runs the webapp with `REALTIME_STREAMS_DEFAULT_VERSION` set to v2
against a live S2, so the pre-fix result is not a configuration gap: the run is
stamped v1, S2 holds nothing, and the record sits in Redis.
Exposes the harness Redis connection so a test can assert the backend directly
rather than inferring it from an absence of records in S2.
Matt Aitken
1826f9a73a