fix: set parent page title before print for correct PDF filename

Chrome/Edge uses parent page title (not iframe title) when printing
to PDF. Temporarily swap document.title to translated stem before
print(), restore it 1s later after dialog opens.

docutranslate/static/index.html

@@ -2010,18 +2010,14 @@
                     const printTitle = match ? match[1].replace(/\.[^.]+$/, '') : '';
                     return r.text().then(h => ({ h, printTitle }));
                 }).then(({ h, printTitle }) => {
-                    if (printTitle) {
-                        if (/<title>/i.test(h)) {
-                            h = h.replace(/<title>[^<]*<\/title>/i, `<title>${printTitle}</title>`);
-                        } else {
-                            h = h.replace(/<head>/i, `<head><title>${printTitle}</title>`);
-                        }
-                    }
                     ifr.srcdoc = h;
                     ifr.onload = () => {
                         setTimeout(() => {
                             ifr.contentWindow.focus();
+                            const originalTitle = document.title;
+                            if (printTitle) document.title = printTitle;
                             ifr.contentWindow.print();
+                            setTimeout(() => { document.title = originalTitle; }, 1000);
                         }, 500);
                     };
                 });