fix(pdf): clear text layer before re-render to stop duplicated spans (v0.5.3)

TextLayer appends into the container without clearing it, so any
re-render of the same page doc (zoom settle, spread-scale update)
stacked a second span set at sub-pixel-shifted positions — selection
text reads doubled. Clear the container (stale spans + previous
endOfContent helper) before each TextLayer render.

pdf.js

@@ -36,6 +36,12 @@ const render = async (page, doc, zoom) => {
   doc.querySelector("#canvas").replaceChildren(doc.adoptNode(canvas));
 
   const container = doc.querySelector(".textLayer");
+  // TextLayer appends into the container without clearing it, so any
+  // re-render of the same page doc (zoom settle, spread-scale update)
+  // stacked a second span set over the old one (sub-pixel shifted —
+  // selection text read doubled). Clear stale spans and the previous
+  // endOfContent helper before rendering fresh.
+  container.replaceChildren();
   const textLayer = new pdfjsLib.TextLayer({
     textContentSource: await page.streamTextContent(),
     container,