fix(docx): bookmark a layer stack's column, so a page reference to it is a field

CHANGELOG.md

@@ -8,6 +8,24 @@ follow semantic versioning; release dates are ISO 8601.
 
 ### Public API
 
+- **A DOCX export bookmarks a layer stack's column, so a page reference or a link to its anchor
+  works.**
+  - A stack whose layers stand side by side is written as a one-row table, each layer's content in
+    its column's cell; the layer itself is not written as a block, and its anchor got no bookmark.
+    A link to it named a bookmark the file did not hold, and a page reference to it was written as
+    the number the layout read, which no edit updates. The bookmark now goes round what the layer
+    writes, from the first paragraph it writes to the last, as a section's or a container's does in
+    the flow. A block of the layer that an earlier layer's stand-in holds — a subtitle drawn in a
+    later layer for the reading order, written in the strip above it — is written there first, and
+    the bookmark opens there.
+  - Measured in Word 16, fields updated, and LibreOffice 24.2, on an anchored column on page 2 and
+    on the same file with a page put in ahead of it: before, both editors read 2 in each and
+    carried no link; now both read 2 and then 3, and the link goes to the column's page. So it is
+    for a left and a right column, a container, a later layer of a column, a column opening with a
+    table, a stack in a panel, and a table of contents' entry.
+  - A column that writes no paragraph — drawings alone — has no bookmark still, and the report
+    names its anchor, as it does a section's of drawings alone.
+
 - **A DOCX export keeps a page break the layout makes by itself after a card where the page
   makes it.**
   - A block kept together or kept with the next in a table cell — a row's column, a panel's cell —

docs/architecture/backend-capability-matrix.md

@@ -103,7 +103,7 @@ Payload records live in `core` under
 | Capability | PDF (fixed) | PPTX (fixed) | DOCX (semantic) |
 |---|---|---|---|
 | External hyperlinks (fragment- and run-level) | ✅ `PdfLinkAnnotationWriter` + link rects in `PdfFixedLayoutBackend` | ✅ `PptxNavigationWriter` (transparent hotspots for measured span, line, and fragment rectangles, emitted above all content after the fragment pass) | ⚠️ `DocxSemanticBackend.newRun` — a paragraph's, a run's, a picture-in-a-line's and a page zone picture's link is a `w:hyperlink` with an external relationship, a run's own link winning over its paragraph's. A block written as a picture, a drawing or a rule — an image, a barcode, a shape, an ellipse, a line — and a table carry none, and the report names the link |
-| Internal links (anchor jump, forward references) | ✅ `PdfInternalLinkWriter` (two-pass) | ✅ `PptxNavigationWriter` (deferred slide-jump hyperlinks, resolved after all fragments — including across sections) | ⚠️ `DocxSemanticBackend` — an internal `linkTarget` is a `w:hyperlink` with `w:anchor`, on what an external one is written on, and every anchor the export writes is a bookmark: a paragraph's around its text, a section's, container's, table's, image's or barcode's around everything the block wrote, a rule's around its paragraph (`bookmarkAround`). A drawing floated over the text — a shape, an ellipse, a line not written as a rule — a stack's layer written as a column, a page zone's paragraph or picture, and a block that writes no paragraph — a section or a container of drawings alone — hold no bookmark: the report names the anchor, a link to it points at no bookmark, and a page reference to it is written as the number the layout found |
+| Internal links (anchor jump, forward references) | ✅ `PdfInternalLinkWriter` (two-pass) | ✅ `PptxNavigationWriter` (deferred slide-jump hyperlinks, resolved after all fragments — including across sections) | ⚠️ `DocxSemanticBackend` — an internal `linkTarget` is a `w:hyperlink` with `w:anchor`, on what an external one is written on, and every anchor the export writes is a bookmark: a paragraph's around its text, a section's, container's, table's, image's or barcode's around everything the block wrote, a stack's layer written as a column around what it writes, a rule's around its paragraph (`bookmarkAround`). A drawing floated over the text — a shape, an ellipse, a line not written as a rule — a page zone's paragraph or picture, and a block that writes no paragraph — a section or a container of drawings alone — hold no bookmark: the report names the anchor, a link to it points at no bookmark, and a page reference to it is written as the number the layout found |
 | Page references — a table of contents' numbers, `addPageReference(...)` (`PageReferenceNode`) | ✅ `PageReferenceDefinition` lays out the resolved page as text, drawn by `PdfParagraphFragmentRenderHandler` | ✅ the same laid-out text through `PptxParagraphFragmentRenderHandler` | ✅ `DocxSemanticBackend.writePageReference` — a `PAGEREF` field to the anchor's bookmark, as a hyperlink (`\h`), storing the page the layout resolved; the editor recomputes it (LibreOffice on layout, Word on a field update). A reference to an anchor the export writes no bookmark for is the text the page prints, since Word turns a `PAGEREF` to a missing bookmark into an error, and the report names it, as it does the margins and padding on the sides its alignment sets it from, which are not written. `w:updateFields` is not set |
 | Document outline / bookmarks tree | ✅ `PdfBookmarkOutlineWriter` | ⚠️ `PptxNavigationWriter` (no PPTX outline concept — slide names where 1:1, extra bookmarks dropped with a note) | ❌ |