fix(openapi): parse YAML responses as binary so the spec sync generates

[subnetmarco]

Summary

The automatic OpenAPI sync from Kong/volcano-hosting (sync-openapi-consumers.yml, job "Sync volcano-sdk-python") has failed on every run, while the CLI, JS, Ruby and web syncs pass. Because of that, the standing chore/sync-openapi PR here stopped updating after 2026-09-19.

Cause. The Hosting spec now documents GET /openapi.yaml (and HEAD), whose 200 response is application/yaml. openapi-python-client can't parse that content type, so it warns:

WARNING parsing GET /openapi.yaml within system.
Cannot parse response for status code 200 (Unsupported content_type {'application/yaml': ...})

scripts/generate_openapi.py runs the generator with --fail-on-warning, so the warning fails the job.

Fix. Add application/yaml: application/octet-stream to content_type_overrides in openapi-python-client.yaml, the same way the binary image types are already handled. The generated operation returns the raw bytes, and the wire Content-Type is unchanged.

Validation

• Reproduced the sync job locally with uv 0.12.17: copied Hosting main's api/openapi.bundled.yaml into openapi/openapi.yaml and ran scripts/generate_openapi.py. It fails on main with the warning above and exits 0 with this change. python -m scripts.check_openapi then reports "OpenAPI generated client is up to date".
• With the repository's current spec, the change leaves the committed generated client untouched (check_openapi passes), so this PR only unblocks the next sync.
• scripts/check_quality_policy.sh passes.

[subnetmarco]

Superseded: main already maps application/yaml to application/octet-stream in openapi-python-client.yaml, so after updating the branch this PR only adds a duplicate key, which the generator rejects ("Unable to parse config").