[BugFix]: CosyVoice3 STFT window device mismatch (#6454)

Signed-off-by: princepride <wangzhipeng628@gmail.com>

vllm_omni/model_executor/models/cosyvoice3/code2wav_core/hifigan.py

@@ -1,5 +1,5 @@
 # SPDX-License-Identifier: Apache-2.0
-# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM-Omni project
 # Adopted from https://github.com/FunAudioLLM/CosyVoice/tree/main/cosyvoice/hifigan
 # Copyright (c) 2024 Alibaba Inc (authors: Xiang Lyu, Kai Hu)
 
@@ -696,7 +696,11 @@ class CausalHiFTGenerator(HiFTGenerator):
         self.ups.apply(init_weights)
         self.conv_post.apply(init_weights)
         self.reflection_pad = nn.ReflectionPad1d((1, 0))
-        self.stft_window = torch.from_numpy(get_window("hann", istft_params["n_fft"], fftbins=True).astype(np.float32))
+        self.register_buffer(
+            "stft_window",
+            torch.from_numpy(get_window("hann", istft_params["n_fft"], fftbins=True).astype(np.float32)),
+            persistent=False,
+        )
         self.conv_pre_look_right = conv_pre_look_right
         self.f0_predictor = f0_predictor