fix(docx): name a page reference's field after its anchor's own bookmark

[DemchaAV]

Why

Since #906, every page reference is written as a PAGEREF field and checked once the body is written. The field was named when the reference was written, through DocxBookmarkNames.nameFor(anchor), so the reference minted its anchor's bookmark name before the anchor's own bookmark did.

Two anchors can clean to the same name, so that order matters. Take a reference to a., an anchor that exists nowhere, followed by paragraphs anchored a and a_2:

• a. took the name a;
• the anchor a was pushed to a_2;
• the anchor a_2 was given a_2 too.

The file held two bookmarks named a_2, so links and fields to either landed wherever Word keeps that name. Before #906, a reference whose anchor got no bookmark minted no name.

What changed

• writePageReference writes the field with no bookmark name and records its instruction (appendField now returns it) together with the reference's anchor. The reference names no bookmark of its own.
• settleThePageReferences replaces unfieldTheReferencesWithoutABookmark. Once every section is written, it names each field after the bookmark its anchor was written under, which openAnchor and bookmarkAround record by anchor. A reference whose anchor got no bookmark is taken back to the number it reads, with its note, as before.
• The unreachable plain-text branch for a blank anchor is gone: PageReferenceNode rejects blank anchors.
• The recipe says when a field is named.

Verification

• New and changed tests:
  • DocxPageReferenceTest:
    • a reference to a. comes before the anchors a and a_2, and the file holds exactly a and a_2, with no field;
    • a reference to a layer stack's column is written as the number it reads;
    • the number left after a field is taken back keeps its run's style (9pt).
  • DocxMultiSectionTest:
    • a reference on the cover to an anchor in the next section is a PAGEREF field;
    • a face set only in the second section's zone is shipped.
• 22 sabotages of fix(docx): read a table's cells, headers and list runs; check page references #906 and of this change each fail a test, among them: the reference minting a name, the fields settled per section instead of after all of them, and only the first section's zones read.
• Template corpus (62 DOCX) against 2.5-dev before fix(docx): read a table's cells, headers and list runs; check page references #906:
  • 59 documents are byte-identical;
  • the 3 that fix(docx): read a table's cells, headers and list runs; check page references #906 changed differ only in the faces it ships;
  • report notes stay 1244 → 1244.
• ./mvnw -B -ntp clean verify → BUILD SUCCESS (render-docx 1628, qa 1820).

Lane: shared-engine (render-docx semantic DOCX backend), no public API change. Follow-up to #906.