修复输出维度计算错误，使用 d_model 代替 input_dim

src/trainer/model.py

@@ -59,7 +59,7 @@ class Expert(nn.Module):
         super().__init__()
         self.input_dim = input_dim
         self.d_model = d_model
-        self.output_dim = input_dim * output_multiplier
+        self.output_dim = d_model * output_multiplier
 
         # 输入映射：input_dim -> d_model
         self.linear_in = nn.Linear(input_dim, d_model)