Safe DOCX posture
w:pBdr paragraph border collection
Declared paragraph borders emit as a w:pBdr collection in the
CT_PBdr sequence (top, left, bottom, right, between, bar)
with explicit size/space/color per edge, sitting in the schema-defined
w:pPr child position (see [ECMA-PART1-17-3-1-26]). The generation
serializer shares one border builder with the table-border collections
so every edge carries the same explicit-attribute discipline.