fix: cast discriminators to model dtype to match vocoder output

Discriminators are constructed as float32 but receive bfloat16 tensors
from the vocoder. Cast to model dtype on load to prevent conv dtype
mismatch in feature matching loss.

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

nodes/selva_bigvgan_trainer.py

@@ -954,8 +954,8 @@ def _do_train(vocoder, mel_converter, clips,
                     f"MPD loaded={mpd_loaded}, MRD loaded={mrd_loaded}. "
                     f"Available keys: {list(ckpt_d.keys())}"
                 )
-            mpd.to(device).eval()
+            mpd.to(device, dtype).eval()
-            mrd.to(device).eval()
+            mrd.to(device, dtype).eval()
             for p in mpd.parameters():
                 p.requires_grad_(False)
             for p in mrd.parameters():