Maps rows, columns, merged ranges, style and placement through the generic
generator (now with tuple and usize support), adds grid/merge/reference
validation, and keeps DXF cell merge dimensions in step with merged_ranges.
staged_python_table_lifecycle_over_real_ipc passes the full gate including
DWG and DXF reopen.
Co-Authored-By: Claude Sonnet 5 <[email protected]>