Let each visibility switch hide only its own thing

The margin notes hung off both switches: `hidden: hideInk || !showPins`, so
turning off the drawing took the markers and their column with it — one switch
turning off both of the things the pair exists to separate.

The checks look at what is actually visible — the ink layer's opacity, how many
markers are on the page, whether the column is there — and test both directions
separately, which is what the old code failed.

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

e2e/pdf.mjs

@@ -759,6 +759,34 @@ try {
   await p.locator("[data-pdf-mode]").click();
   await p.waitForTimeout(700);
 
+  /* Each switch hides its own thing and nothing else. They shared a condition
+     once, so hiding the drawing took the markers and their column with it —
+     one switch turning off both of the things the pair exists to separate. */
+  const drawingShows = async () =>
+    (await p.locator('[data-pdf-ink="1"]').evaluate((c) => getComputedStyle(c).opacity)) !== "0";
+  const marginNotesShow = async () => (await p.locator("[data-pin]").count()) > 0;
+
+  check((await drawingShows()) && (await marginNotesShow()), "both are showing to begin with");
+
+  await p.locator("[data-pdf-hide-ink]").click();
+  await p.waitForTimeout(900);
+  check(!(await drawingShows()), "hiding the drawing hides the drawing");
+  check(await marginNotesShow(), "and leaves the margin notes alone");
+  check(
+    (await p.locator("[data-pdf-margin]").count()) > 0,
+    "including their column",
+    String(await p.locator("[data-pdf-margin]").count())
+  );
+  await p.locator("[data-pdf-hide-ink]").click();
+  await p.waitForTimeout(900);
+
+  await p.locator("[data-pdf-show-pins]").click();
+  await p.waitForTimeout(900);
+  check(!(await marginNotesShow()), "hiding the margin notes hides the margin notes");
+  check(await drawingShows(), "and leaves the drawing alone");
+  await p.locator("[data-pdf-show-pins]").click();
+  await p.waitForTimeout(900);
+
   check((await p.locator("[data-pdf-show-pins]").count()) === 1, "the margin notes can be hidden");
   await p.locator("[data-pdf-show-pins]").click();
   await p.waitForTimeout(1200);

frontend/src/features/pdf/PdfViewer.jsx

@@ -804,7 +804,11 @@ export function PdfViewer({ note, dark, onUpdate, onPagesReady, notesToggle, foc
                   notes: notesForPage(ink, i + 1),
                   placing,
                   openId: openPin,
-                  hidden: hideInk || !showPins,
+                  // Only the margin-note switch decides this. It used to read
+                  // `hideInk || !showPins`, so hiding the drawing took the
+                  // markers and their column with it — one switch turning off
+                  // both things the pair was meant to separate.
+                  hidden: !showPins,
                   withMargin,
                   onOpen: setOpenPin,
                   onPlace: placeNote,