fix(docx-core): preserve live section and mark properties when rejecting pPrChange

[stevenobiajulu]

Independent dynamic Opus 5 review of PR #980 head25ff4870 found a pre-existing native Reject discrepancy: rejecting pPrChange replaces all of pPr with its CT_PPrBase snapshot, losing live paragraph-mark rPr and sectPr. Comparison AST retains those non-base children correctly.

Reviewer control requires no paragraph merge or mark revision: one paragraph with pPrChange (old jc=both), live rPr/color=FF0000 and sectPr/pgSz. Native rejectChanges yields only jc=both; rejectAllChanges retains the mark color and section. The affected native PhaseF restoration is untouched by PR #980 (current reject_changes.ts around637).

• Reproduce independently on main with a schema-valid synthetic standalone paragraph.
• Preserve live non-CT_PPrBase children during property snapshot restoration; test section topology and mark formatting separately.
• Cover selected and foreign-author property revisions, empty snapshots, and adjacent sections.
• Require native/AST parity, XSD validation and full gates before shipping a repair.

Prioritize section-topology loss above cosmetic empty-rPr cleanup#982. No fix included in PR#980. Word behavior remains unverified; public/synthetic inputs only.

Ref: #941, PR #980 review N1.