GFQL deletion: remove Cypher reentry compiletime lowering-symbol shim #1471

Summary

The Cypher reentry extraction still preserves behavior through a broad compatibility shim: graphistry/compute/gfql/cypher/reentry/compiletime.py imports cypher.lowering and runs globals().update(vars(_lowering)) so extracted functions can keep using lowering-private symbols.

That was useful during the S3/#1260 split, but it is now a concrete deletion/refactor surface.

Current evidence

On current origin/master:

• graphistry/compute/gfql/cypher/reentry/compiletime.py says it preserves behavior and compatibility via lowering-level shims.
• The module does from graphistry.compute.gfql.cypher import lowering as _lowering and globals().update(vars(_lowering)).
• graphistry/compute/gfql/cypher/lowering.py still comments that reentry helpers are re-exported there for compatibility.

Goal

Make reentry compiletime explicit and self-contained enough to delete the broad symbol-table shim and any stale lowering-level reexports that are no longer needed.

Scope

• Identify all symbols from lowering that reentry/compiletime.py really uses.
• Replace globals().update(vars(_lowering)) with explicit imports or local helpers.
• Remove stale reexports/import compatibility comments where tests show no public need.
• Keep behavior identical for bounded reentry compilation.
• Update split-guard tests so future broad symbol-table shims are caught.

Out of scope

• Semantic changes to reentry execution.
• New Cypher feature support.
• Reopening [META] GFQL deletion wave: remove 2K+ LOC of obsolete compatibility paths #1419.

Acceptance

• No globals().update(vars(_lowering)) shim remains in reentry compiletime.
• Any remaining lowering-level compatibility reexports are justified by tests or removed.
• Focused reentry/lowering tests pass.
• Broad GFQL and tck-gfql CI pass; run DGX GFQL/cuDF if changed code reaches runtime.

Related

• Meta: GFQL monolith shrinkdown (lowering.py + CompiledCypher cleanup) #1260
• [META] GFQL deletion wave: remove 2K+ LOC of obsolete compatibility paths #1419
• GFQL compat-executor reachability shrink #1467