fix: download-all returns error on partial failures (#50)

* fix: return error from --download-all when downloads fail

downloadAllAttachments was returning nil even when individual file
downloads failed, causing the CLI to exit 0. Callers (and scripts)
had no way to detect partial failures.

* fix: also return error in JSON output path

The --json code path returned early before the error check,
so download failures with --json still exited 0.

Co-authored-by: gemini-code-assist[bot] <gemini-code-assist[bot]@users.noreply.github.com>

---------

Co-authored-by: gemini-code-assist[bot] <gemini-code-assist[bot]@users.noreply.github.com>

Author: Hinne1

internal/cmd/confluence/page/attachment.go

@@ -313,7 +313,13 @@ func downloadAllAttachments(opts *AttachmentOptions, confluence *api.ConfluenceS
 			Downloads: downloads,
 			Errors:    errors,
 		}
-		return output.JSON(opts.IO.Out, result)
+		if err := output.JSON(opts.IO.Out, result); err != nil {
+			return err
+		}
+		if len(errors) > 0 {
+			return fmt.Errorf("failed to download %d attachment(s)", len(errors))
+		}
+		return nil
 	}
 
 	if len(errors) > 0 {
@@ -324,6 +330,9 @@ func downloadAllAttachments(opts *AttachmentOptions, confluence *api.ConfluenceS
 	}
 
 	fmt.Fprintf(opts.IO.Out, "\nDownloaded %d of %d attachments to %s\n", len(downloads), len(attachments), opts.OutputDir)
+	if len(errors) > 0 {
+		return fmt.Errorf("failed to download %d attachment(s)", len(errors))
+	}
 	return nil
 }