Add guide metadata, redesign PDF cover, paginate steps per-page, and run exports in a helper process

Lets users record author/co-authors/organization for a guide via a new
"Guide information…" dialog; this metadata renders below the title on
the PDF cover (title now sits above the accent rule). PDF export also
paginates so each step fits its own page where possible, keeps a
step's title/image/lead-in together, and forces the next step onto a
fresh page after an oversized step overflows. Exports now run in a
forked helper process so large guides no longer freeze the UI.

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

exporters/pdf.js

@@ -130,8 +130,11 @@ function exportPdf(ast, outDir, template = {}) {
   const images = tpl.includeImages ? renderAllImages(ast) : new Map();
 
   let y = M;
+  // Never start a page break when already at the top of a page — an item
+  // taller than a full page (e.g. a step's combined head height) must
+  // still render and overflow naturally rather than push out a blank page.
   const ensure = (needed) => {
-    if (y + needed > size.height - M) {
+    if (y > M && y + needed > size.height - M) {
       pdf.addPage();
       y = M;
     }
@@ -169,14 +172,79 @@ function exportPdf(ast, outDir, template = {}) {
     }
   };
 
+  /** Height a callout block (emitBlock) will occupy, including its trailing gap. */
+  const measureBlock = (tb) => {
+    const { height: bodyH } = tb.descriptionHtml
+      ? layoutDescription(pdf, tb.descriptionHtml, usableW - 18, 9.5)
+      : { height: 0 };
+    return 16 + bodyH + 6;
+  };
+
+  /** Height an image will occupy on the page, including its trailing gap. */
+  const measureImage = (stepId) => {
+    const img = images.get(stepId);
+    if (!img) return 0;
+    const maxH = usableH * tpl.imageMaxHeightRatio;
+    let h = (img.height / img.width) * usableW;
+    if (h > maxH) h = maxH;
+    return h + 10;
+  };
+
+  const measureCode = (block) => {
+    const lines = String(codeBlockText(block) || '').split('\n');
+    const lineH = 9 * 1.3;
+    return lines.length * lineH + 16;
+  };
+
+  const measureTable = (block) => {
+    if (!block.rows || !block.rows.length) return 0;
+    return block.rows.length * 16 + 8;
+  };
+
+  /**
+   * Compute the vertical space a step will need: `head` is the title, the
+   * accent rule, any before-description blocks, the description, and the
+   * image — kept together on one page — and `total` adds the remaining
+   * blocks plus the trailing gap, used to decide whether the whole step
+   * fits on a fresh page.
+   */
+  const measureStep = (step) => {
+    const headSize = step.depth > 0 ? 12 : 14;
+    const titleText = `${step.number}. ${step.title || 'Untitled step'}${step.skipped ? '  (skipped)' : ''}`;
+    const titleLines = pdf.wrapText(titleText, headSize, usableW, 'F2');
+    let head = Math.max(40, titleLines.length * headSize * 1.35 + 8);
+
+    const { before, rest } = stepContentGroups(step);
+    for (const tb of before) head += measureBlock(tb);
+    if (step.descriptionHtml) head += layoutDescription(pdf, step.descriptionHtml, usableW, 10.5).height;
+    head += measureImage(step.stepId);
+
+    let restHeight = 0;
+    for (const block of rest) {
+      if (block.kind === 'text') restHeight += measureBlock(block);
+      else if (block.kind === 'code') restHeight += measureCode(block);
+      else if (block.kind === 'table') restHeight += measureTable(block);
+    }
+
+    return { head, total: head + restHeight + 10 };
+  };
+
   pdf.addPage();
 
   if (tpl.includeCover) {
     y = M + usableH * 0.18;
-    pdf.rect(M, y - 18, usableW, 3, { fill: tpl.accentColor });
-    y += 6;
-    writeLines(ast.guide.title, { size: 26, font: 'F2' });
-    y += 8;
+    writeLines(ast.guide.title, { size: 28, font: 'F2' });
+    y += 10;
+    pdf.rect(M, y, usableW, 3, { fill: tpl.accentColor });
+    y += 16;
+    const meta = ast.guide.metadata || {};
+    const metaLines = [
+      meta.author && `Author: ${meta.author}`,
+      meta.coAuthors && `Co-authors: ${meta.coAuthors}`,
+      meta.organization && `Organization: ${meta.organization}`,
+    ].filter(Boolean);
+    for (const line of metaLines) writeLines(line, { size: 11, color: [90, 90, 90] });
+    if (metaLines.length) y += 8;
     if (ast.guide.descriptionHtml) writeDescription(ast.guide.descriptionHtml, { size: 12, color: [70, 70, 70] });
     y += 14;
     writeLines(`${ast.steps.length} steps — generated ${ast.generatedAt.slice(0, 10)}`, { size: 10, color: [120, 120, 120] });
@@ -197,10 +265,23 @@ function exportPdf(ast, outDir, template = {}) {
   }
 
   let first = true;
+  let forcedFresh = false;
+  const pageBottom = size.height - M;
   for (const step of ast.steps) {
-    if (step.forceNewPage && !first) { pdf.addPage(); y = M; }
+    const { head: headHeight, total: totalHeight } = measureStep(step);
+    // Start a fresh page when: the step's "New page" toggle is set; the
+    // previous step overflowed past one page (so this step shouldn't share
+    // the spillover page); or this step doesn't fit in what's left of the
+    // current page. The last check is skipped when already at the top of a
+    // page, so an overlong step doesn't push out a blank page first.
+    const needsFreshPage = !first && (
+      step.forceNewPage || forcedFresh || (y > M && y + totalHeight > pageBottom)
+    );
+    if (needsFreshPage) { pdf.addPage(); y = M; }
     first = false;
-    ensure(40);
+    // Keep the title, accent rule, lead-in blocks, description, and image
+    // together — never split across a page boundary.
+    ensure(headHeight);
     pdf.bookmark(`${step.number}. ${step.title || 'Untitled step'}`);
     const headSize = step.depth > 0 ? 12 : 14;
     writeLines(`${step.number}. ${step.title || 'Untitled step'}${step.skipped ? '  (skipped)' : ''}`, { size: headSize, font: 'F2' });
@@ -259,6 +340,7 @@ function exportPdf(ast, outDir, template = {}) {
     }
 
     y += 10;
+    forcedFresh = totalHeight > usableH;
   }
 
   function emitBlock(tb) {