fix(pdf): hand pdfjs a file:// standardFontDataUrl; repair Windows CI tests

pdfjs validates standardFontDataUrl as a URL ending in a forward slash —
our raw path with a trailing path.sep is invalid on Windows (C:\...\),
failing extractText/extractImages (and every test that verifies through
them) with 'Invalid factory url: must include trailing slash'. Linux and
macOS passed only because / is also a valid URL slash. Convert with
pathToFileURL() so every platform sends file:///.../standard_fonts/.

Also escape path.sep in PDFBatchOperations' sanitizer test regex — a bare
backslash made new RegExp() a syntax error on Windows.

tests/main/PDFBatchOperations.test.js

@@ -293,7 +293,9 @@ describe('PDFBatchOperations - runPDFBatchOperation', () => {
         operation: 'compress',
         outputFolder: path.join(blocker, 'child'),
         data: {},
-        sanitizeError: (message) => message.replace(new RegExp(path.sep, 'g'), '_SANITIZED_'),
+        // path.sep is "\" on Windows — escape it for RegExp use
+        sanitizeError: (message) =>
+          message.replace(new RegExp(path.sep.replace(/\\/g, '\\\\'), 'g'), '_SANITIZED_'),
       });
 
       expect(completion.success).toBe(false);