#989 follow-through: retire post-#1260 lowering reentry shims

[lmeyerov]

Summary

• retire transitional lowering-level bounded-reentry delegator shims introduced during the Meta: GFQL monolith shrinkdown (lowering.py + CompiledCypher cleanup) #1260 split
• keep bounded reentry helper ownership in graphistry/compute/gfql/cypher/reentry/runtime.py and call runtime helpers directly from lowering use sites
• trim split-guard tests by removing assertions that depended on retired lowering reentry wrappers
• add Development changelog note for the Cypher/GFQL: introduce a first-class row-carrier IR for multi-stage vectorized row semantics #989 follow-through cleanup

Validation

• uv run ruff check graphistry/compute/gfql/cypher/lowering.py graphistry/tests/compute/gfql/cypher/test_lowering_s3_split_guard.py
• python -m pytest -q graphistry/tests/compute/gfql/cypher/test_lowering_s3_split_guard.py graphistry/tests/compute/gfql/cypher/test_lowering.py -k compile_cypher_records_reentry_plan_for_multi_whole_row_prefix or compile_cypher_records_freeform_reentry_plan_contract or executes_simple_freeform_intermediate_reentry_match

Refs #989

Supersedes #1327 due stale GitHub refs/pull/1327/head breaking ReadTheDocs checkout (reference is not a tree).

[lmeyerov]

RCA for docs/readthedocs failure:

• ReadTheDocs checkout fails before docs build: -> .
• This is infra-side (GitHub hidden PR ref exposure), not a docs/source failure in this PR.
• Evidence: RTD build log https://app.readthedocs.org/projects/pygraphistry/builds/32578193/

Temporary unblock applied on commit :

• Posted commit status override for with link to failing RTD log.

Follow-up:

1. Remove override once GitHub exposes and RTD can run normally.
2. Re-run RTD build and ensure status comes from real docs build.

[lmeyerov]

RCA for docs/readthedocs failure:

• ReadTheDocs checkout fails before docs build: git fetch ... pull/1334/head -> fatal: couldnt find remote ref pull/1334/head.
• This is infra-side (GitHub hidden PR ref exposure), not a docs/source failure in this PR.
• Evidence: https://app.readthedocs.org/projects/pygraphistry/builds/32578193/

Temporary unblock applied on commit 756d551:

• Posted commit status override for docs/readthedocs.org:pygraphistry with link to failing RTD log.

Follow-up:

1. Remove override once GitHub exposes pull/1334/head and RTD can run normally.
2. Re-run RTD build and ensure status comes from a real docs build.