Implement Round 4 Parakeet model selection

Ariver

2026-06-03 62f9a3b1e84455c32971272c03163ca543e2f68f

 privatevoice.src/internal/engine/engine_darwin.go

@@ -62,6 +62,11 @@
      config.ModelConfig.Moonshine.Encoder = resolved.Files["encoder"]
      config.ModelConfig.Moonshine.UncachedDecoder = resolved.Files["uncached_decoder"]
      config.ModelConfig.Moonshine.CachedDecoder = resolved.Files["cached_decoder"]
   case model.BackendNemoTransducer:
      config.ModelConfig.Transducer.Encoder = resolved.Files["encoder"]
      config.ModelConfig.Transducer.Decoder = resolved.Files["decoder"]
      config.ModelConfig.Transducer.Joiner = resolved.Files["joiner"]
      config.ModelConfig.ModelType = model.BackendNemoTransducer
   default:
      return sherpa.OfflineRecognizerConfig{}, fmt.Errorf("unsupported backend kind: %s", resolved.BackendKind)
   }