build(wasm): deploy the REAL pdfium-engine.wasm with reflow fixes (caret x0, center/right)

The live-preview engine the frontend loads is pdfium-engine.wasm, built by the
`wasm-pdfium` CMake preset (PDFENGINE_WITH_PDFIUM=ON). The reflow code is inside
`#ifdef PDFENGINE_WITH_PDFIUM`, so the `wasm` stub preset (PDFium OFF) — which
scripts/build_wasm.ps1 builds and copies to the UNUSED pdfengine.wasm — never
contained reflow at all. Result: every prior "WASM rebuilt" step updated the wrong,
reflow-less artifact, so the caret x0 fix (and center/right) never reached the browser.

Rebuilt the wasm-pdfium preset and deployed bin/pdfengine.{mjs,wasm} ->
public/pdfium-engine.{mjs,wasm} (md5 now 53d1ec9f, reflow object 631KB vs the 18KB
stub). Bumped the cache-buster so browsers fetch the new engine.

Engine .pyd + overlay-diff gate unchanged (1.70%/1.69%, render identical); the x0
change is caret-only metadata.

Follow-up: build_wasm.ps1 builds the wrong (stub) preset and deploys the wrong file.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/lib/pdfiumEngine.ts

@@ -23,7 +23,7 @@ function getModule(): Promise<PdfiumModule | null> {
   if (!modulePromise) {
     modulePromise = (async () => {
       try {
-        const V = '20260617c';
+        const V = '20260617d';
         const resp = await fetch(`/pdfium-engine.mjs?v=${V}`, { cache: 'no-store' });
         if (!resp.ok) throw new Error(`pdfium-engine.mjs ${resp.status}`);
         const blobUrl = URL.createObjectURL(new Blob([await resp.text()], { type: 'text/javascript' }));