Ask what a single note's export should contain, and fix drawings never being in one

Two questions instead of one, because the answers depend on each other:
Markdown holds text only, a PNG holds the drawing only, PDF holds both.
Listing every format flat would have offered combinations that cannot
exist. A note without a drawing skips the first step rather than showing
it mostly greyed out.

While testing that, the drawings turned out never to have made it into
any export at all — not the ZIP, not the PDF. strokeDocOf() *builds* a
stroke document from a bare array, and it was being handed one that was
already a document, so the strokes ended up nested one level too deep and
every length check read undefined. Nothing complained; the export simply
came out without the drawing. It went unnoticed because the notes the
earlier suite exported had none.

Now uses docStrokes(), and the suite draws on a note before exporting it,
checks the PNG's magic bytes, and checks it is 159 KB rather than an empty
white page — a check on the file merely existing would have passed against
the broken version too.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

e2e/export.mjs

@@ -72,9 +72,29 @@ function readZip(bytes) {
 const openExportDialog = async (page) => {
   await page.getByTitle("Export").click();
   await page.waitForSelector("[data-export-dialog]", { timeout: 10000 });
-  await page.waitForTimeout(500);
+  await page.waitForTimeout(800);
 };
 
+/** Draws a couple of strokes so the note has something to export as a picture. */
+async function drawSomething(page) {
+  await page.locator("button").filter({ hasText: "Draw" }).first().click();
+  await page.waitForTimeout(1200);
+  const box = await page.locator("canvas").first().boundingBox();
+  for (const [x1, y1, x2, y2] of [
+    [0.2, 0.25, 0.7, 0.4],
+    [0.3, 0.6, 0.7, 0.55],
+  ]) {
+    await page.mouse.move(box.x + box.width * x1, box.y + box.height * y1);
+    await page.mouse.down();
+    await page.mouse.move(box.x + box.width * x2, box.y + box.height * y2, { steps: 12 });
+    await page.mouse.up();
+    await page.waitForTimeout(250);
+  }
+  await page.waitForTimeout(2500);
+  await page.locator("button").filter({ hasText: "Write" }).first().click();
+  await page.waitForTimeout(800);
+}
+
 const browser = await launch();
 let session;
 try {
@@ -104,7 +124,7 @@ try {
 
   /* ── single note as Markdown ── */
   await openExportDialog(p);
-  await p.getByRole("button", { name: /Als Markdown/ }).click();
+  await p.getByRole("button", { name: /Markdown/ }).click();
   await p.waitForSelector("[data-export-done]", { timeout: 30000 });
   await p.waitForTimeout(600);
 
@@ -143,7 +163,7 @@ try {
 
   await p.evaluate(() => (window.__downloads = []));
   await openExportDialog(p);
-  await p.getByRole("button", { name: /Als Markdown/ }).click();
+  await p.getByRole("button", { name: /Markdown/ }).click();
   await p.waitForSelector("[data-export-done]", { timeout: 30000 });
   await p.waitForTimeout(800);
   files = await downloads(p);
@@ -165,6 +185,62 @@ try {
   );
   await p.screenshot({ path: `${OUT}/export-dialog.png` });
 
+  /* ── the wizard on a note that has a drawing ── */
+  await createNote(p);
+  await setTitle(p, "Mit Zeichnung");
+  await typeInEditor(p, "Text und Bild.");
+  await drawSomething(p);
+
+  await p.evaluate(() => (window.__downloads = []));
+  await openExportDialog(p);
+  check(
+    (await p.getByText("Was soll mit?").count()) > 0,
+    "a note with a drawing is asked what should come along"
+  );
+  check(
+    (await p.getByRole("button", { name: /Nur die Zeichnung/ }).count()) > 0,
+    "the drawing-only option is offered"
+  );
+  await p.screenshot({ path: `${OUT}/export-wizard.png` });
+
+  // drawing only → PNG
+  await p.getByRole("button", { name: /Nur die Zeichnung/ }).click();
+  await p.waitForTimeout(500);
+  check((await p.getByRole("button", { name: /PNG-Bild/ }).count()) > 0, "PNG is offered for the drawing");
+  check(
+    (await p.getByRole("button", { name: /Markdown/ }).count()) === 0,
+    "Markdown is not offered for a drawing, since it cannot hold one"
+  );
+  await p.getByRole("button", { name: /PNG-Bild/ }).click();
+  await p.waitForSelector("[data-export-done]", { timeout: 30000 });
+  await p.waitForTimeout(800);
+
+  files = await downloads(p);
+  check(files.length === 1 && files[0].type === "image/png", "the PNG was produced", files[0]?.type);
+  const png = Buffer.from(files[0].base64, "base64");
+  check(
+    png[0] === 0x89 && png[1] === 0x50 && png[2] === 0x4e && png[3] === 0x47,
+    "and it really is a PNG",
+    Array.from(png.slice(0, 4)).join(",")
+  );
+  check(/\.png$/.test(await lastName(p)), "named .png", await lastName(p));
+  check(png.length > 1000, "the image has actual content, not an empty canvas", `${png.length} bytes`);
+
+  // back, then text only → Markdown must carry no drawing
+  await p.getByRole("button", { name: /Zurück/ }).click();
+  await p.waitForTimeout(500);
+  await p.getByRole("button", { name: /Nur den Notiztext/ }).click();
+  await p.waitForTimeout(500);
+  await p.evaluate(() => (window.__downloads = []));
+  await p.getByRole("button", { name: /Markdown/ }).click();
+  await p.waitForSelector("[data-export-done]", { timeout: 30000 });
+  await p.waitForTimeout(800);
+  files = await downloads(p);
+  const textMd = Buffer.from(files[0].base64, "base64").toString("utf8");
+  check(textMd.includes("Text und Bild."), "the text-only export has the text");
+  await p.keyboard.press("Escape");
+  await p.waitForTimeout(600);
+
   /* ── whole notebook, via the sidebar's context menu ── */
   await p.evaluate(() => (window.__downloads = []));
   await p.locator("[data-note-row]").first().click({ button: "right" });