fix: a header/footer zone keeps its blank lines and its logo's height

A letterhead header is usually a couple of empty lines, the logo, then one
more — the empty leading ones were dropped on import, and the body's content
area counted every line as one text line, logo included. Page 1 of a contract
form started 19mm too high.

src/lib/components/Editor.svelte

@@ -66,9 +66,16 @@
   const HF_LINE_PX = 16 * 1.15;
   function hfReachPx(doc: HfDoc, distPx: number): number {
     if (!doc || hfIsEmpty(doc)) return 0;
-    const inline = ((doc.content?.[0] as { content?: { type?: string }[] } | undefined)?.content ?? []);
-    const lines = 1 + inline.filter((n) => n.type === 'hardBreak').length;
-    return distPx + lines * HF_LINE_PX;
+    const inline = ((doc.content?.[0] as { content?: { type?: string; attrs?: { height?: number } }[] } | undefined)?.content ?? []);
+    // Per line, since an as-character image (a letterhead logo) makes its own line
+    // as tall as it is; the others are one text line each.
+    let total = 0;
+    let image = 0;
+    for (const n of inline) {
+      if (n.type === 'hardBreak') { total += Math.max(HF_LINE_PX, image); image = 0; }
+      else if (n.type === 'image' && typeof n.attrs?.height === 'number') image = Math.max(image, n.attrs.height);
+    }
+    return distPx + total + Math.max(HF_LINE_PX, image);
   }
   let footerDistPx = $derived(cmToPx((hfDistances ?? DEFAULT_HF_DISTANCES).footer));
   let headerDistPx = $derived(cmToPx((hfDistances ?? DEFAULT_HF_DISTANCES).header));

src/lib/import/docx.ts

@@ -1613,11 +1613,12 @@ function convertHfPart(relId: string | null, ctx: Ctx): HfDoc {
   const relsPath = path.replace(/^word\/(.*)$/, 'word/_rels/$1.rels');
   const hfCtx: Ctx = { ...ctx, rels: parseRels(ctx.files[relsPath]) };
 
-  const inline: Node[] = [];
+  // One line per source paragraph, joined by hard breaks below: an empty leading line
+  // is a line of the zone too, and the body starts under the whole of it.
+  const lines: Node[][] = [];
   let textAlign: string | null = null;
   const boxMaps: Record<string, string>[] = [];
   for (const p of hfParagraphs(root)) {
-    if (inline.length) inline.push({ type: 'hardBreak' });
     const ppr = fc(p, 'pPr');
     if (textAlign === null) {
       const ta = (fc(ppr, 'jc') ? wVal(fc(ppr, 'jc')!) : null) ?? '';
@@ -1628,12 +1629,17 @@ function convertHfPart(relId: string | null, ctx: Ctx): HfDoc {
     // The zone carries no styleName and no style CSS reaches it, so the yardstick is the
     // editor's own defaults — what the Header/Footer style provides has to become marks
     // (mirrors odt.ts convertHfZone, which passes no style name either).
-    inline.push(...convertInline(p, hfCtx, baseRun, blockDefaults({}, null, false), true).filter((n) => n.type !== PB_MARKER));
+    lines.push(convertInline(p, hfCtx, baseRun, blockDefaults({}, null, false), true).filter((n) => n.type !== PB_MARKER));
   }
   // An all-empty zone is dropped unless it carries a background/rule line (a footer that
   // is just a colored line has no text). The zone collapses to one paragraph (mergeHfBox).
   const box = mergeHfBox(boxMaps);
-  if (inline.length === 0 && Object.keys(box).length === 0) return null;
+  if (lines.every((l) => l.length === 0) && Object.keys(box).length === 0) return null;
+  const inline: Node[] = [];
+  lines.forEach((line, i) => {
+    if (i) inline.push({ type: 'hardBreak' });
+    inline.push(...line);
+  });
 
   const para: Node = { type: 'paragraph', content: inline };
   const attrs: Record<string, string> = {};