Round 19 reviewer consensus (3/10 plus an asymmetric-fix call-out
across rounds 8/9/12/14/17): the openai-python SDK ships
service_tier as Literal["auto","default","flex","scale","priority"]
on /v1/responses, and enterprise Scale Tier customers need to opt in
explicitly. Drop the defensive scale-filter on the backend and add
"scale" to the OpenAI picker option list so the field reaches the
wire when set. Other providers remain at auto/default per their docs.
Update the routing tests so `scale` lives in the forwarded-set fixture
and the dropped-set fixture only carries truly out-of-enum values
(Anthropic-only `standard_only`, typos, empty string).
b961c6f2f7