## What changed
- The realtime startup-context tests no longer assume the interesting
websocket payload is always `connection 1 / request 0`.
- Instead, they now wait for the first outbound websocket request that
actually carries `session.instructions`, regardless of which websocket
connection won the accept-order race on the runner.
- The env-key fallback test stays serialized because it mutates process
environment.
## Why this fixes the flake
- The old test synchronized on the mirrored `session.updated` client
event and then inspected a fixed websocket slot.
- On CI, the response websocket and the realtime websocket can race each
other during startup. When the response websocket wins that race, the
fixed slot can contain `response.create` instead of the
startup-context-bearing `session.update` request the test actually cares
about.
- That made the test fail nondeterministically by inspecting the wrong
request, or by timing out waiting on a secondary event even though the
real outbound request path was correct.
- Waiting directly on the first request whose payload includes
`session.instructions` removes both ordering assumptions and makes the
assertion line up with the actual contract under test.
- Separately, serializing the environment-mutating fallback case
prevents unrelated tests from seeing partially updated auth state.
## Scope
- Test-only change.
Ahmed IbrahimandGitHub
75e608343c