fix(docx): hold the space above a list, a line pair and a band's table on a new page

CHANGELOG.md

@@ -8,6 +8,26 @@ follow semantic versioning; release dates are ISO 8601.
 
 ### Public API
 
+- **A DOCX export keeps the space above a list, a line pair, and a table, a row or a panel
+  opening a band, on the page the layout moves them to.** Word drops the space above a paragraph
+  at the top of a page. A paragraph, a picture and a spacer there already hold theirs in a line
+  kept with them; these did not.
+  - Measured in Word and LibreOffice on Windows, each moved to a new page:
+    - a list with a 14pt margin stood 14pt high, and so did one opening a stack of one layer or a
+      band with a 14pt margin; a list padded 10pt, or opening a section padded 10pt, stood 10pt
+      high;
+    - a title and its dates set as one line in a stack with a 14pt margin stood 14pt high, in the
+      flow and opening a band;
+    - a row, a table or a panel opening a band with a 14pt margin stood 14pt high: the band's
+      margin was left at the foot of the page above.
+  - Each now holds that space in a line kept with it, as a paragraph does. A list and a line pair
+    stand within 0.1pt of a paragraph moved so; a row, a table and a panel within 0.1pt of the same
+    block moved to a new page in the flow. A list's wrapped first item takes the gap between its
+    lines out of that line, as a paragraph does there, and stands where such a paragraph does. A
+    row, a table or a panel opening a band holds the band's margin above it with its own, and the
+    gap before the band stays at the foot of the page above, as one in the flow leaves it. A line
+    pair whose text the page sets above its overlay's top is left as it was.
+  - None of the corpus's 62 DOCX changes, and none of its 1246 notes.
 - **A DOCX export sets a later layer where the page does when its first block's edge reaches
   above the layers before it.** A layer written after another starts at the page's gap below
   them, less what its first block writes above its content itself. Where the block held more

docs/architecture/backend-capability-matrix.md

@@ -122,7 +122,7 @@ honour an option ignores it (documented contract).
 | Protection / encryption | ✅ `PdfDocumentPostProcessor` | ❌ (ignored with a one-time warning — no OOXML encryption support planned) | ❌ (not written, so the file opens unprotected; reported `DROPPED`, `protection`) |
 | Viewer preferences | ✅ `applyViewerPreferences` in `PdfFixedLayoutBackend` | ❌ (ignored with a one-time warning — PDF-viewer concept) | n/a (not written; reported `DROPPED`, `viewer preferences`) |
 | Debug guide lines / node labels | ✅ `PdfGuideLinesRenderer`, `PdfNodeLabelRenderer` | ❌ (ignored with a one-time warning — render through the PDF backend to see overlays) | n/a |
-| Keep a block on one page (`keepTogether()`, `keepWithNext()`) | ✅ resolved by `LayoutCompiler` before any backend runs | ✅ same — the slides are the laid-out pages | ✅ `DocxSemanticBackend.keepOnOnePage` — Word re-paginates, so a block the layout placed on one page is told to stay there: `w:keepLines` on each of its paragraphs and `w:keepNext` on every one but the last (on the last too for `keepWithNext`), a table inside it chained row by row. A layer stack or a shape container in the flow is kept so too, as the layout moves it to a new page whole, a band of layers included; the first block of a band the layout moves to a new page — a paragraph, a picture or a spacer, a backdrop drawn before it or not — holds the space above it there, as one in the flow does: in a line kept with it, or in a spacer's own line. A block that ran over a page break in the layout is taller than a page and is left to flow, as the layout left it. A body table of one row kept with what follows, its cells holding paragraphs alone, is written with a row that may break (`letTheOneRowTablesKeptWithTheNextBreak`): LibreOffice reads a one-row table whose row may not break as one that may not split, and keeps such a table with nothing |
+| Keep a block on one page (`keepTogether()`, `keepWithNext()`) | ✅ resolved by `LayoutCompiler` before any backend runs | ✅ same — the slides are the laid-out pages | ✅ `DocxSemanticBackend.keepOnOnePage` — Word re-paginates, so a block the layout placed on one page is told to stay there: `w:keepLines` on each of its paragraphs and `w:keepNext` on every one but the last (on the last too for `keepWithNext`), a table inside it chained row by row. A layer stack or a shape container in the flow is kept so too, as the layout moves it to a new page whole, a band of layers included; the first block of a band the layout moves to a new page — a paragraph, a picture, a list, a title and its dates set as one line or a spacer, a backdrop drawn before it or not — holds the space above it there, as one in the flow does: in a line kept with it, or in a spacer's own line; a table, a row or a panel opening it holds the band's top edge so with its own, the gap before the band left at the foot of the page above. A list or such a line the layout moves to a new page in the flow holds its space above there as a paragraph does. A block that ran over a page break in the layout is taller than a page and is left to flow, as the layout left it. A body table of one row kept with what follows, its cells holding paragraphs alone, is written with a row that may break (`letTheOneRowTablesKeptWithTheNextBreak`): LibreOffice reads a one-row table whose row may not break as one that may not split, and keeps such a table with nothing |
 | Layer stack — layers drawn over one another (`addLayerStack`) | ✅ each layer's fragments at the place the layout gave it | ✅ same | ⚠️ `DocxSemanticBackend` — Word has no layers, so a stack's children are written one after the other, without their positions. The exception is a stack whose layers are side-by-side columns (`DocxLayerColumns`): every layer a plain container at the stack's top-left corner, the bands their padding leaves either the same or apart. That is written as one table row, a cell per band, the way a two-column CV lays its columns out as layers to draw the name first. Layers sharing a band follow one another in its cell. A spacer the layout placed level with content of another layer of the same band only keeps that content's place, and is not written. The space above a later layer's first block is the gap the page shows below the content before it, to the block's content: what the block holds above that content past the gap — its margin, its padding, a contained picture's room — comes out of its own edge (`DocxLayerColumns.resume`) where it is a paragraph, a picture, a list or a table in its layer's own flow with its edge above at zero or more, and a list keeps its own edges after the gap, as a table does. Each layer is held to its box across, past the stack's edge where the page sets it past it, by an indent below zero; in a table cell no further left than the indents round it give, the rest named. The one layer of a stack of one layer is held the same way, its offset across kept and its measure with it; in a table cell, composed in a table's cell with no place of its own, and for an offset down or up, which moves it without making room for it, it is written where the stack starts and named — not where a band or a column's layer sets it at the page's distance below what is above it, which holds the offset. A shape container written as a panel in a table cell keeps its padding round its outline, as the page does — the table's indent and the space above and below it; where its table ends its cell, Word sets the cell's content at its middle or foot without the space below, which a centred cell takes off the space above, the rest named — sets what its cell holds at the top, middle or foot as its first written layer is set, holds a paragraph across to its box, and names a written layer after the first (written under the ones before it), an offset down or up, a box past the shape's side, and a layer set across by a box the layout does not give (`layer offset`). A layer whose content the page starts above where those before it end — a caption over its photo, a label in a card's corner, not a block giving back its edge whose padding or contained picture's room alone reaches there — is written under them, in a column's cell as in a band, and the report names it; a stack composed in a table cell, or exported with no layout, has no place of its own, and one writing more than one of its layers is named with them not measured. What the page draws inside another layer's fill comes after that fill. Drawings stack as the page paints them, by their z-index, each given its place (`wp:anchor/@relativeHeight`) from where the page paints its fragment, whatever order the layers are written in — among the drawings behind the text, and among those in front of it, as Word draws every one behind under every one in front. Measured in LibreOffice: `CharcoalGold`, `SidebarPortrait` and `SlateOrange` fit on one page, as on the page; `NavySidebar` runs one line onto a second page. A stack or shape container the page gives no room — its margins taking back its whole height, as `LumaStudioInvoice`'s sidebar over the page's top margin — is laid over the flow (`laidOverTheFlow`): its drawings where the page draws them, each paragraph in a text box in front of the text where the page sets it, nothing in the flow. Not in a table cell or a panel, and not when it holds anything but drawing and plain paragraphs — a link, an anchor, a picture, a list or a table keeps it in the flow as above. A canvas is written as its contents — what it writes one block after another, its drawings where it places them — and holds its height: the room under what it writes is the space below it, and one that only draws holds its whole box where nothing round it — a band before its layer's first block, drawings held whole, an overlay it is a layer of — measures that room already. The report names the places and the width it loses, as it does a column's fixed width narrower than its band, and what it writes running past its height, a drawing in what it writes that takes no room in Word, or a height not measured |
 
 ## Output surface and lifecycle