feat: execute GFQL RETURN pipeline for Cypher TCK promotions

[lmeyerov]

Summary

• add deterministic promotion sweep with row-plan execution
• add constrained match(pattern=...) compiler path for simple Cypher graph pattern handling
• add plan parameter binding for expression arguments and SKIP/LIMIT
• add mixed-type Cypher-style ORDER BY sort keys
• add Expr(func) allowlist including temporal constructors used by promoted scenarios

Validation

• PYTHONPATH=/home/lmeyerov/Work/tck-gfql:/home/lmeyerov/Work/pygraphistry pytest -q tests/cypher_tck/test_tck_runner.py
  • on main (0c3a796): 14 passed, 3613 xfailed
  • on feat/return-pipeline-exec (3675f82): 548 passed, 3079 xfailed
  • delta: +534 passed, -534 xfailed

Notes

• phase 2.6 confirms no new pygraphistry runtime execution path was added in this branch; changes are in tck harness/compiler/executor surface.