[codex] Remove connected-match row-join compat fallback - #1431

Summary

Refs #1418.

Conservative D1 deletion: remove the legacy connected MATCH row-join fallback branch from the compatibility executor. Connected MATCH joins now route directly from the physical-plan executor before generic same-path/row-pipeline compatibility dispatch, so they no longer re-enter the old compat executor branch.

Kept out of scope intentionally:

• connected OPTIONAL MATCH compatibility shim, because optional-wavefront is still marked converging and pyg-bench#12/[POST-RERUN] #880 residual: tag-cooccurrence join-aggregation bucket #1415 remains benchmark-side ambiguous
• CALL compatibility shim
• general same_path/row_pipeline compatibility dispatch for non-connected-match shapes

Validation

• /tmp/tck-gfql-ci-venv312/bin/python -m pytest -q graphistry/tests/compute/gfql/test_runtime_physical_cutover.py
• /tmp/tck-gfql-ci-venv312/bin/python -m pytest -q graphistry/tests/compute/gfql/cypher/test_lowering.py::test_issue_1411_connected_join_property_projection_shape graphistry/tests/compute/gfql/cypher/test_lowering.py::test_issue_1411_connected_join_whole_row_projection_shape
• /tmp/tck-gfql-ci-venv312/bin/python -m pytest -q graphistry/tests/test_compute_chain.py::TestChainBindingsTable::test_issue_1411_join_apply_projects_joined_message_rows graphistry/tests/test_compute_chain.py::TestChainBindingsTable::test_issue_1411_join_apply_left_preserves_unmatched_rows
• ./bin/ruff.sh graphistry/compute/gfql_unified.py graphistry/tests/compute/gfql/test_runtime_physical_cutover.py

No benchmark reruns were run locally.