fixup: 🌱 Improve E2E error reporting

The reasoning behind this change was not clear. I added a comment to
explain it.

end-to-end/utils_test.go

@@ -157,6 +157,12 @@ func distroIsProAttached(t *testing.T, ctx context.Context, d gowsl.Distro) (boo
 	var stdout, stderr bytes.Buffer
 
 	cmd := d.Command(ctx, "pro status --format=json")
+
+	// We need separate Stdout and Stderr. We cannot combine them because the
+	// pro client prints warnings to Stderr, which makes the combined output
+	// invalid JSON. We also cannot ignore either:
+	// - We need StdOut to parse the JSON output.
+	// - We need Stderr to read the error message in case the command fails.
 	cmd.Stdout = &stdout
 	cmd.Stderr = &stderr