feat(pdf-tools): add attachments feature to embed files in PDFs

Implement new functionality to allow embedding attachments into PDF documents. The feature includes:
- UI for selecting PDF and files to attach
- Logic to embed files while preserving metadata
- Display of attached files with size information
- Download of modified PDF with embedded files

src/tests/pdf-tools.test.ts

@@ -19,7 +19,7 @@ describe('Tool Configuration Arrays', () => {
 
     it('should have the correct number of tools', () => {
       // This acts as a snapshot test to catch unexpected additions/removals.
-      expect(singlePdfLoadTools).toHaveLength(39);
+      expect(singlePdfLoadTools).toHaveLength(40);
     });
 
     it('should not contain any duplicate tools', () => {