fix: 修复保存路径解析逻辑，统一使用 resolve() 处理 saveto 参数

src/pptopic/lib.py

@@ -116,7 +116,7 @@ def PPT_longPic(
                 new_img = img.resize((nwidth, nheight), resample=Image.Resampling.LANCZOS)
                 canvas.paste(new_img, box=(0, (i - 1) * nheight))
 
-        filepath = pptFile.parent if Path(saveto) == Path(".") else Path(saveto)
+        filepath = Path(saveto).resolve()
         if saveName:
             if Path(saveName).suffix:
                 canvas.save(filepath / saveName)