fix(cypher): run exact ic6 tag cooccurrence - #1037

Summary

• stack the exact IC6 follow-on on top of fix(cypher): support joined-row aggregate overlap #1036
• attach scalar-prefix reentry state to the terminal compiled stage that actually consumes it
• allow connected multihop bindings rows to carry undirected and branching endpoint rows while preserving bare alias ids for row filters
• add exact IC6, multihop row-binding, and direct rows(binding_ops=...) regressions

Validation

• python3 -m pytest -q graphistry/tests/compute/gfql/cypher/test_lowering.py -k "issue_1000_ic6_exact_runtime_minimal or issue_1000_ic6_compiles_after_phase6_connected_star_fanout or recent_message_reentry_multihop_branching_row_bindings or undirected_multihop_row_bindings or remaining_unsupported_multihop_row_bindings" -> 6 passed, 644 deselected
• python3 -m pytest -q graphistry/tests/compute/gfql/cypher/test_lowering.py -k "connected_multi_pattern or connected_star_comma_fanout or scalar_only_prefix_with_match_reentry or multiple_post_with_where_clauses or post_with_match_collect_unwind_match or issue_1000_ic6_compiles_after_phase6_connected_star_fanout or issue_1000_ic6_exact_runtime_minimal or multihop_row_bindings or recent_message_reentry_multihop" -> 38 passed, 6 skipped, 606 deselected
• python3 -m pytest -q graphistry/tests/compute/gfql/cypher/test_parser.py -k "reentry or unwind" -> 11 passed, 84 deselected
• python3 -m pytest -q graphistry/tests/test_compute_chain.py -k "undirected_bounded_multihop_without_backtracking or bare_alias_token_expressions or named_multihop_edge_alias or open_range_multihop_continuation or reverse_bounded_range_multihop_continuation" -> 6 passed, 64 deselected
• ruff check graphistry/compute/gfql/cypher/lowering.py graphistry/compute/gfql/row/pipeline.py graphistry/tests/compute/gfql/cypher/test_lowering.py graphistry/tests/test_compute_chain.py -> passed
• uv run python scripts/run_dgx_spark_suite.py --suite snb-interactive --config configs/suites/snb-interactive-ic6-conformance-sf1.yaml --output-dir results/runs/dgx-spark-issue-1000-ic6-1037 --graphistry-repo-path /home/lmeyerov/Work/pygraphistry2 --host-uv -> cypher = ok, gfql = partial
• ssh -tt dgx-spark 'cd /tmp/$USER-pygraphistry-e1aa3dfa && RAPIDS_IMAGE=nvcr.io/nvidia/rapidsai/base:26.02-cuda13-py3.13 PROFILE=gfql WITH_GPU=1 WITH_IMAGE_BUILD=0 TEST_FILES="graphistry/tests/compute/gfql/cypher/test_lowering.py::test_string_cypher_executes_undirected_multihop_row_bindings_on_cudf graphistry/tests/compute/gfql/cypher/test_lowering.py::test_string_cypher_executes_recent_message_reentry_multihop_scalar_projection_on_cudf" ./docker/test-rapids-official-local.sh' -> 2 passed

Refs #1000