fix: update file upload body type in MineruPreprocessProvider

- Changed the body of the fetch request from a Buffer to a Uint8Array to ensure proper handling of binary data during PDF uploads.

src/main/knowledge/preprocess/MineruPreprocessProvider.ts

@@ -273,7 +273,7 @@ export default class MineruPreprocessProvider extends BasePreprocessProvider {
 
       const response = await fetch(uploadUrl, {
         method: 'PUT',
-        body: fileBuffer,
+        body: new Uint8Array(fileBuffer),
         headers: {
           'Content-Type': 'application/pdf'
         }