Closes #1499

Summary

• Added graphistry.compute.gfql.row.frame_ops for active row-table construction, empty-frame construction, rows, drop_cols, skip, limit, and distinct.
• Kept the existing RowPipelineMixin method surface as delegates so row-pipeline call dispatch remains unchanged.
• Added a Development/Internal changelog entry.

Scope / behavior

• Mechanical modularization only. No new GFQL/Cypher semantics.
• Avoids the active GFQL/Cypher: extract reentry helper ownership out of lowering.py #1497 reentry-helper, GFQL temporal_text.py: split temporal parsing/folding domains #1498 temporal text, GFQL deletion: remove residual unplanned Cypher chain fallback after bucket closeout #1486 fallback deletion, and chore(gfql): remove unused cypher lowering helper #1500 lowering audit lanes.

Validation

• python3 -m py_compile graphistry/compute/gfql/row/frame_ops.py graphistry/compute/gfql/row/pipeline.py
• python3 -m pytest -q graphistry/tests/compute/gfql/test_row_pipeline_ops.py -k "row_pipeline_exec_projection_sort_page_distinct or row_pipeline_rows_validation or row_pipeline_skip_limit_validation or row_pipeline_distinct_validation or drop_cols" -> 10 passed
• python3 -m pytest -q graphistry/tests/compute/gfql/test_row_pipeline_ops.py -k "not cudf" -> 183 passed, 17 deselected
• python3 -m pytest -q graphistry/tests/compute/gfql/cypher/test_lowering.py -k "issue_996_limit or issue_996_skip_limit or issue_996_distinct or compiled_query_sets_logical_plan_route_for_distinct_projection_shape or string_cypher_supports_constant_limit_expressions or string_cypher_supports_integer_division_in_limit_expression" -> 6 passed
• ./bin/ruff.sh graphistry/compute/gfql/row graphistry/tests/compute/gfql/test_row_pipeline_ops.py
• ./bin/typecheck.sh graphistry/compute/gfql/row
• python3 bin/ci_cypher_surface_guard.py
• DGX isolated tree ~/repos/pygraphistry-1499-validation-20260517: RAPIDS 26.02 test_row_pipeline_ops.py -k cudf -> 17 passed, 183 deselected
• DGX isolated tree ~/repos/pygraphistry-1499-validation-20260517: RAPIDS 25.02 test_row_pipeline_ops.py -k cudf -> 17 passed, 183 deselected; known numba-cuda driver-version warning only

Review skill

• Review artifacts under plans/issue-1499-row-pipeline-modularization/ locally.
• Wave 1: 0 blocker, 0 important, 0 suggestion.
• Wave 2: 0 blocker, 0 important, 0 suggestion.
• Converged after two clean waves.

Notes

• First DGX attempt against ~/repos/pygraphistry failed before tests because that clone is detached/dirty and older than this branch base (same_path_types.NODE_IDENTITY_COLUMN missing). Final DGX validation used an isolated synced tree instead of resetting the shared clone.
• Do not auto-merge; coordinator requested PR open but not merged.