fix(docx): count a spacer's hairline in its height

CHANGELOG.md

@@ -8,6 +8,14 @@ follow semantic versioning; release dates are ISO 8601.
 
 ### Public API
 
+- **A spacer is as tall in DOCX as on the page.** A spacer is written as an empty paragraph a
+  tenth of a point tall, which Word keeps (measured: ten such lines between eleven lines of
+  text added 0.96pt), and its whole height was then owed below it as well. Every spacer stood a
+  tenth of a point taller than the page's; `EditorialBlue`'s first page ran 1.2pt low by its
+  foot, its last entry's heading found no room there in Word, and its second page stood 10pt
+  low. The spacer's height now counts its own line. `EditorialBlue`'s lines more than 2pt off
+  fall from 9 to none in Word and in LibreOffice on Windows, and the corpus's mean drift in
+  Word from 0.49 to 0.45pt.
 - **A body paragraph or spacer the layout moves to a new page keeps the space above it there
   in DOCX.** The page starts a paragraph a page break moves down at its own top edge, with the
   containers opening there, and keeps the gap before it too where the gap did not fit at the

docs/recipes/docx-export.md

@@ -76,7 +76,7 @@ creation date is real metadata.
 | Links and anchors | A `linkTarget` becomes a `w:hyperlink` — a relationship for an address, `w:anchor` for one of the document's own anchors — and a run's own link wins over the paragraph's — in a list item as much as in a paragraph. An `anchor(...)` becomes a bookmark wrapping that paragraph's text, named as Word requires; on a section, container, table or image it wraps everything the block wrote, from the start of its first paragraph to the end of its last, so a link to a block lands on its first line. A `bookmark(...)` outline level becomes Word's own `HeadingN` style, which is what puts the paragraph in the Navigation Pane, the outline view and a generated table of contents. The style states the outline level and nothing else, so the paragraph keeps its own formatting. The role comes from what the document declared, never from how big the text is |
 | Rows | A one-row table spanning the content width — or only its columns, where fixed columns leave part of the row empty — so editors keep the side-by-side layout. The row's slots become the column grid when they are weights, an even split or fixed columns; fixed columns that add up to less than the row leave the rest of it empty, the last one at its own width and the table no wider than its columns, so its text wraps where the page wraps it; the gap and the row's padding ride in the neighbouring column and come back out as that cell's margin; a cell holds whatever its child is, written as it is anywhere else. The row's `verticalAlign` is every cell's `w:vAlign`, so a child shorter than the row sits at its middle or bottom as on the page — a table of contents' leader on its entry's baseline. The row is kept whole across a page break, as the layout keeps it. A row is held at least as tall as the page makes it inside a painted panel, and anywhere its tallest child is a drawing Word holds nothing of in its cell — a badge beside a heading. A section or other container in any cell — a row's, a table's, a panel's — that pulls its first line up with a negative top edge writes that one-line paragraph as much shorter, its text seated where the page sets it — no more than the room above its letters, as Word draws an exact line's text only inside the line |
 | Sections / containers | Children written in order. A timeline with its markers on the rail (`markerOnRail()`) lays each entry's body out in the header row's content column, below the row; the body is written in the flow, indented to that column where the page puts it. A container with a fill, per-side borders or a uniform stroke is a one-cell table carrying them, its padding as the cell's margins, so a card keeps its panel — see "What a panel keeps and loses" below. A `keepTogether()` or `keepWithNext()` block the layout placed on one page stays on one page in Word too (`w:keepLines` + `w:keepNext`, and a row that may not split for a panel) |
-| Spacers | An empty paragraph a tenth of a point tall; the spacer's height is the space above the next block, or below this paragraph when a table follows. A spacer in the body the layout moves to a new page with the gap before it, because the gap did not fit at the foot of the page above, holds the space the layout leaves above it there — that gap, and the edges of any containers opening with it — in its line, which Word keeps at the top of a page where it drops the space above |
+| Spacers | An empty paragraph a tenth of a point tall, which Word keeps (a shorter spacer stands that tenth); the rest of the spacer's height is the space above the next block, or below this paragraph when a table follows. A spacer in the body the layout moves to a new page with the gap before it, because the gap did not fit at the foot of the page above, holds the space the layout leaves above it there — that gap, and the edges of any containers opening with it — in its line, which Word keeps at the top of a page where it drops the space above |
 | Page breaks | Explicit Word page breaks |
 
 Page geometry (size, margins and orientation — a page wider than it is tall is stated as