[lmeyerov]

Summary

• Adds hermetic old/current GFQL HTTP-route contract tests for GFQL remote: test generated client wire against old and current server handlers #2248, covering public Let, serialized Let, compiled Cypher Let, and nonempty flat Chain.
• Asserts JSON/parquet success and typed old-server declines, with exact row/edge oracles and public-client typed preflight errors that send no HTTP request.
• Pins old server 054e79c87d74a87dbd68c40d4d43a9a6e23f61c3 and current server 72d2664c2e61859cb813cb94c6479e3bc0824291; fixtures source-map the route boundary to local execution. This is contract evidence, not deployed Hub acceptance.

Verification

• PR exact head: 814f94a78fbcce93d772809321b73775e272698c
• Tree/base: 98a29296b3c928531d877d788f9f6f499016fcbd / a196caa43f57a5bdf4be7abca76f051c04204b85
• Local focused tests: 8 passed, 6 skipped (intentional paired-fixture skips)
• ruff check graphistry/tests/compute/gfql/routes/test_old_current_server_wire_2248.py: passed
• git diff --check a196caa43f57a5bdf4be7abca76f051c04204b85 814f94a78fbcce93d772809321b73775e272698c: passed
• Exact-head CI: run 40261831275 SUCCESS
• Exact-head CodeQL: run 40261831260 SUCCESS
• Exact-head RTD: build 35402057 Finished/success
• No tag/release/deployment/publication.