feat(cypher): support comma-separated node-only MATCH - #1019

Summary

Implements #990 by supporting comma-separated node-only Cypher MATCH cartesian products in the local compiler.

Closes #990
Prerequisite for #1010

What changed

• lower disconnected comma-separated node-only MATCH clauses without forcing them through the connected-path stitcher
• materialize cartesian bindings rows through rows(binding_ops=...) for node-only alias sets
• support scalar projection, cross-alias row filters, grouped/global aggregates, and staged WITH over those cartesian rows
• fall back from the simple graph-projection path to general row execution for cartesian multi-alias expressions like RETURN n.ts < m.ts AS lt
• teach static schema validation that rows(binding_ops=...) exposes alias-backed row columns

Tests

• added RED/GREEN regressions for cartesian scalar projection, grouped/global count, cross-alias WHERE, staged WITH, and non-simple scalar expressions in graphistry/tests/compute/gfql/cypher/test_lowering.py
• added direct rows(binding_ops=[Node, Node]) cartesian row-materialization coverage in graphistry/tests/test_compute_chain.py

Verification

• python3.12 -B -m pytest -q graphistry/tests/test_compute_chain.py -k 'ChainBindingsTable' -> 36 passed, 32 deselected
• python3.12 -B -m pytest -q graphistry/tests/compute/gfql/cypher/test_lowering.py -k 'cartesian_node_only or multi_alias_return or multi_alias_with_stage_still_rejected or cypher_to_gfql_supports_multi_alias_scalar_projection' -> 19 passed, 544 deselected