isModelOnDisk method
Whether the GGUF model + its sibling tokenizer.json are already on
disk for the given spec. Used by the cold-start restore path so the
screen can skip the download UX when nothing actually needs downloading.
Implementation
Future<bool> isModelOnDisk(SyniModelSpec spec) async {
final dir = await _modelsDir();
final modelFile = File('${dir.path}/${spec.filename}');
final tokenizerFile = File('${dir.path}/tokenizer.json');
return modelFile.existsSync() && tokenizerFile.existsSync();
}