[codex] Remove stale reentry failfast scaffolding - #1433

Summary

Refs #1421.

• remove the obsolete graphistry.compute.gfql.cypher.reentry.runtime compatibility re-export shim
• move tests off stale private reentry compatibility import paths
• lift the stale closed-Cypher/GFQL: forward bounded-reentry carry hidden columns across reentry-source rebinding (LDBC SNB IC3) #1256 chained-reentry aggregate failfast and convert the two regression locks to positive row assertions
• keep active unsupported-shape failfasts, including secondary whole-row bare-alias carry guards

Validation

• python3 -m pytest -q graphistry/tests/compute/gfql/cypher/test_lowering.py -k "chained_reentry_carry_with_aggregate"
• python3 -m pytest -q graphistry/tests/compute/gfql/cypher/test_lowering.py -k "chained_reentry_carry_with_aggregate or secondary_whole_row_return or non_source_alias_is_bare_referenced"
• python3 -m pytest -q graphistry/tests/compute/gfql/test_ir_type_propagation.py::TestSeamWith1303LoweringSplit::test_post_1303_modules_and_t3_helpers_coimport graphistry/tests/compute/test_gfql.py::TestGFQLCypherReentryCarrier -k "not cudf"
• python3 -m pytest -q graphistry/tests/compute/gfql/cypher/test_lowering.py -k "reentry and not cudf"
• ./bin/ruff.sh graphistry/compute/gfql/cypher/lowering.py graphistry/compute/gfql/cypher/reentry graphistry/tests/compute/gfql/cypher/test_lowering.py graphistry/tests/compute/gfql/test_ir_type_propagation.py graphistry/tests/compute/test_gfql.py
• ./bin/typecheck.sh graphistry/compute/gfql/cypher/lowering.py graphistry/compute/gfql/cypher/reentry
• git diff --check

Local caveats:

• cudf tests are not runnable on this host because cudf imports but no CUDA device is available (cudaErrorNoDevice); GPU/cuDF coverage should be taken from CI or dgx-spark.
• ./bin/test-minimal-lite.sh --ignore=plans reaches unrelated installed-cudf/CuPy/UMAP no-CUDA failures on this host.
• tck-gfql is left to CI.

Review Plan

Continuing with the requested .agents/skills/review/SKILL.md loop after PR creation:

• credentials scan
• multi-wave review until two consecutive no-advance waves
• CI watch/fix loop until green
• periodic origin/master drift check, with special attention to CHANGELOG.md