fix: _do_optimize returns dict not tuple — prevent double-wrapping AUDIO output

optimize() does return (_result[0],) to wrap for ComfyUI. _do_optimize was
returning (dict,) instead of dict, causing double-wrapping: ((dict,),).
ComfyUI then received a tuple as audio and failed on audio["waveform"].

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

nodes/selva_ditto_optimizer.py

@@ -459,4 +459,4 @@ def _do_optimize(net_generator, feature_utils, mel_converter,
             audio = audio / peak
 
     print(f"[DITTO] audio: shape={tuple(audio.shape)} sr={sample_rate}", flush=True)
-    return ({"waveform": audio.cpu(), "sample_rate": sample_rate},)
+    return {"waveform": audio.cpu(), "sample_rate": sample_rate}