feat: add OmniVoiceModelLoader node

Implements OmniVoiceModelLoader with INPUT_TYPES, RETURN_TYPES, and
load_model supporting both HuggingFace auto-download and local path
sources. Adds TDD test suite and pytest infrastructure (conftest.py,
pytest.ini) to enable testing outside ComfyUI without omnivoice installed.

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

tests/test_loader.py

@@ -0,0 +1,59 @@
+# tests/test_loader.py
+from unittest.mock import patch, MagicMock
+import torch
+import pytest
+from nodes.loader import OmniVoiceModelLoader
+
+
+def test_input_types_structure():
+    inputs = OmniVoiceModelLoader.INPUT_TYPES()
+    required = inputs["required"]
+    assert "model_source" in required
+    assert "device" in required
+    assert "dtype" in required
+    optional = inputs.get("optional", {})
+    assert "local_path" in optional
+
+
+def test_input_types_model_source_choices():
+    inputs = OmniVoiceModelLoader.INPUT_TYPES()
+    choices = inputs["required"]["model_source"][0]
+    assert "Auto-download (HuggingFace)" in choices
+    assert "Local path" in choices
+
+
+def test_return_type():
+    assert OmniVoiceModelLoader.RETURN_TYPES == ("OMNIVOICE_MODEL",)
+
+
+def test_load_model_auto_download():
+    loader = OmniVoiceModelLoader()
+    mock_model = MagicMock()
+    with patch("nodes.loader.OmniVoice") as MockOmniVoice:
+        MockOmniVoice.from_pretrained.return_value = mock_model
+        result = loader.load_model(
+            model_source="Auto-download (HuggingFace)",
+            device="cpu",
+            dtype="float32",
+            local_path="",
+        )
+    assert result == (mock_model,)
+    MockOmniVoice.from_pretrained.assert_called_once()
+    call_kwargs = MockOmniVoice.from_pretrained.call_args
+    assert call_kwargs[0][0] == "k2-fsa/OmniVoice"
+
+
+def test_load_model_local_path():
+    loader = OmniVoiceModelLoader()
+    mock_model = MagicMock()
+    with patch("nodes.loader.OmniVoice") as MockOmniVoice:
+        MockOmniVoice.from_pretrained.return_value = mock_model
+        result = loader.load_model(
+            model_source="Local path",
+            device="cpu",
+            dtype="float32",
+            local_path="/some/local/path",
+        )
+    assert result == (mock_model,)
+    call_args = MockOmniVoice.from_pretrained.call_args[0][0]
+    assert call_args == "/some/local/path"