docs: the ODF import yardstick is the default style, and its spacing exception

src/lib/import/CLAUDE.md

@@ -18,7 +18,8 @@ The **Open .odt** button (`App.svelte`) parses an uploaded file with `importOdt(
 - **A complex-script run takes the `-complex` font and size** (`complexScriptProps`). ODF carries western, asian and complex properties side by side and a word processor picks per character, so a Hebrew paragraph whose style declares only `style:font-size-complex="16pt"` is set at 16pt — read as the western 12pt its line pitch comes out 1.6mm short of LibreOffice's. Decided per **run**, the finest split the model has, so a document with no complex script is untouched; our own export writes all three alike, so the value round-trips.
 - **Hidden text is not laid out.** `text:display="none"` drops the paragraph a paragraph style hides (with a warning) and the stored value of a field element that carries the attribute. A hidden **heading** is the exception and renders: it is the document's outline, which the running head's `text:chapter` reads (an ODF chapter marker exists for nothing else), and the editor has no way to hold a block it does not draw.
 - **A run is measured against the block's own size**, not the yardstick's: a list item whose style sets 11pt would otherwise drop every 12pt run as "the style supplies it" and render it at 11 (`convertParaLike`, `runDefaults`).
-- **The yardstick is the style the block can name.** Only a **body** block carries a `styleName`, so a paragraph in a cell or a text box is measured against the *default* paragraph style instead of its own — otherwise everything its style provides is suppressed as "the style will supply it" and nothing ever does (a Word caption in a text box arrived without its italic or its colour).
+- **The yardstick is the style the block can name.** Only a **body** block carries a `styleName`, so a paragraph in a cell or a text box is measured against the *default* paragraph style instead of its own — otherwise everything its style provides is suppressed as "the style will supply it" and nothing ever does (a Word caption in a text box arrived without its italic or its colour). It must be the default style and not the editor's fallback: `p:not([data-style])` re-applies exactly that, so a cell paragraph's `fo:line-height="100%"` under a 115% `Standard` is real direct formatting. **Spacing is the exception** — `:is(td, th) > p:not([data-style])` outranks the style's rule and zeroes it, so a cell paragraph's margins stay direct; a list item's `li p` rule loses on specificity and a heading is not a `p` at all, so neither zeroes.
+- **`style:contextual-spacing`** drops a paragraph's own spacing towards a neighbour of the same style (LibreOffice's `List` styles carry it; Word's `w:contextualSpacing` is the same rule). The editor has no such mode, so the suppressed side becomes an explicit 0 — and in a list, where each item wraps its own paragraph, the neighbour is the adjacent *item's*.
 - **Default suppression** keeps round trips (editor → LibreOffice → editor) from accreting explicit attrs: values matching the editor's defaults (12pt body, `HEADING_STYLE_OVERRIDES` sizes/margins, **0 paragraph spacing**, list margin 0, Times New Roman/Liberation Serif, `#000000` text) are imported as `null`/no mark, with small tolerances for producer unit rounding (pt↔cm↔twips). This is why the editor's defaults must equal Word's/LibreOffice's (below) — an editor-only default is indistinguishable from a failed style resolution and silently lands in every imported document.
 - **A heading is bold by default only where the bold built-in still renders it.** `blockDefaults` suppresses a run mark the block's style supplies, and the editor's `Heading` parent supplies bold — but a file that declares its own heading style re-parents it to `Standard` (`collectStyleSheet`), so nothing supplies bold there and an explicit `w:b` / `fo:font-weight` has to stay a mark or the heading renders regular. Gated on the style's own `w:basedOn` / `style:parent-style-name` (`styleBasedOn`, `styleParent`), which is exactly what decides whether the built-in's parent survives.
 - **Mapping:** `text:h` → heading (level clamped to `MAX_HEADING_LEVEL`), per-depth `text:list-level-style-*` defs decide bullet vs ordered and `listStyleType` (reverse lookup `orderedTypeFromFormat`), tables handle covered cells / `number-columns-repeated` / header rows / colspans / cell shading (`StyleResolver.cellBackgroundColor` → `backgroundColor`) / cell borders (`StyleResolver.cellBorders` + `borderAttrFromOdf` → the per-side border attrs) / table margins (`tableMargins` reads the table style's `fo:margin-*`, `style:width`/`style:rel-width` and `table:align` against `Ctx.contentWidthCm` — so a table narrower than the text width stays narrow instead of being stretched; DOCX does the same from `w:tblInd` + the `w:tblGrid`/`w:tblW` width), `text:s`/`text:tab`/`text:line-break` become spaces/`\t`/`hardBreak`, `draw:frame`/`draw:image` → an `image` node (`convertFrame`: bytes read from the zip's `Pictures/` entry into a data-URI, `svg:width`/`-height` cm → px, `svg:title` → `alt`, `draw:transform` rotate → `rotation`; a non-`as-char` anchor or a graphic style's `style:wrap` → floating `wrap` mode via `StyleResolver.graphicProps` — an **explicit `as-char` anchor is always inline**: LibreOffice's named Graphics style carries a `style:wrap` that would otherwise float every inherited frame), text fields keep their stored value. **Text boxes / shapes** (`convertDrawElement`): `draw:frame`+`draw:text-box` → a `textBox` node (`convertTextBoxFrame`: height = `fo:min-height` else `svg:height`; fill/stroke read straight from `graphicProps`' `draw:fill(-color)`/`draw:stroke`/`svg:stroke-*`, values equal to the editor defaults suppressed, none → explicit `null`); `draw:rect`/`draw:ellipse`/`draw:custom-shape` with a rect/round-rectangle/ellipse preset → a `textBox` with the matching `shapeKind` (`convertShape`), and `draw:polygon`/`polyline`/`path`/`connector` — or a preset no gallery covers but whose `draw:enhanced-path` is a plain outline — → a box carrying that outline as `shapePath` (`convertFreeform`, `docs/architecture/frames.md`; a geometry built from modifier formulas still reads as "Unsupported shapes were removed"). A box is a block node but its frame sits inside a `text:p`, so converted boxes ride `Ctx.pendingBlocks` and `convertBlocks` flushes them after the anchor paragraph (dropping our own export's empty anchor); in cells/other boxes their blocks are unwrapped in place with a warning. The DOCX importer mirrors all of this — its drawing root is the `w:drawing`'s **direct** `wp:inline`/`wp:anchor` child, since a box holding a picture nests a second drawing and a subtree search reads *its* root instead, dropping the box and the caption in it (`convertWpsShape` for DrawingML `wps:wsp` — probed before the image `a:blip` path, `convertPict` for legacy VML; Word's `mc:AlternateContent` uses only the `mc:Choice` branch so the VML fallback can't double-import).