feat: add DiffRhythm eval-model download script

Add arty script to download eval.yaml and eval.safetensors files from
HuggingFace space for DiffRhythm node support. These files are required
for DiffRhythm evaluation model functionality.

- Add models/diffrhythm-eval script to download eval-model files
- Update setup/comfyui-nodes to create eval-model directory
- Files downloaded from ASLP-lab/DiffRhythm HuggingFace space
- Script includes file verification and size reporting

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

arty.yml

@@ -312,7 +312,7 @@ scripts:
 
     # Create DiffRhythm model directories
     echo "Creating DiffRhythm model directories..."
-    mkdir -p $COMFYUI_ROOT/models/TTS/DiffRhythm/{MuQ-large-msd-iter,MuQ-MuLan-large,xlm-roberta-base}
+    mkdir -p $COMFYUI_ROOT/models/TTS/DiffRhythm/{MuQ-large-msd-iter,MuQ-MuLan-large,xlm-roberta-base,eval-model}
 
     # Fix numpy version for vLLM compatibility
     echo "Fixing numpy version..."
@@ -327,6 +327,35 @@ scripts:
     echo "  - Impact-Pack: Face enhancement"
     echo "  - DiffRhythm: Full-length song generation"
 
+  models/diffrhythm-eval: |
+    echo "========================================="
+    echo "  Downloading DiffRhythm Eval Model"
+    echo "========================================="
+    echo ""
+
+    # Create eval-model directory
+    mkdir -p $COMFYUI_ROOT/models/TTS/DiffRhythm/eval-model
+    cd $COMFYUI_ROOT/models/TTS/DiffRhythm/eval-model
+
+    # Download eval.yaml (129 bytes)
+    echo "Downloading eval.yaml..."
+    curl -L -o eval.yaml "https://huggingface.co/spaces/ASLP-lab/DiffRhythm/resolve/main/pretrained/eval.yaml"
+
+    # Download eval.safetensors (101 MB)
+    echo "Downloading eval.safetensors (101 MB)..."
+    curl -L -o eval.safetensors "https://huggingface.co/spaces/ASLP-lab/DiffRhythm/resolve/main/pretrained/eval.safetensors"
+
+    # Verify files
+    if [ -f "eval.yaml" ] && [ -f "eval.safetensors" ]; then
+      echo ""
+      echo "✓ DiffRhythm eval-model files downloaded successfully"
+      echo "  - eval.yaml: $(du -h eval.yaml | cut -f1)"
+      echo "  - eval.safetensors: $(du -h eval.safetensors | cut -f1)"
+    else
+      echo "❌ ERROR: Failed to download eval-model files"
+      exit 1
+    fi
+
   setup/comfyui-extensions-deps: |
     echo "========================================="
     echo "  Installing ComfyUI Extensions Dependencies"