feat: add project structure and basic NNUE model

- Create python directory with data/, model/ subdirectories
- Implement LinearEval(61072->1) model
- Add config, constants, feature_extractor
- Add tests with 4 passing test cases

python/tests/test_nnue.py

@@ -0,0 +1,45 @@
+"""Tests for NNUE implementation"""
+
+import pytest
+import torch
+import numpy as np
+from python.model.nnue_linear import LinearEval
+from python.constants import TOTAL_FEATURES
+
+
+class TestLinearEval:
+    """Tests for the linear NNUE model"""
+
+    def test_model_initialization(self):
+        """Test model creates correct shape"""
+        model = LinearEval()
+        assert model.linear.in_features == TOTAL_FEATURES
+        assert model.linear.out_features == 1
+
+    def test_model_output_shape(self):
+        """Test model outputs correct shape"""
+        model = LinearEval()
+        x = torch.randn(10, TOTAL_FEATURES)
+        y = model(x)
+        assert y.shape == (10, 1)
+
+    def test_model_zero_output(self):
+        """Test model with zero input"""
+        model = LinearEval()
+        x = torch.zeros(1, TOTAL_FEATURES)
+        with torch.no_grad():
+            y = model(x)
+        assert y.item() == 0.0
+
+    def test_gradient_flow(self):
+        """Test gradients flow through model"""
+        model = LinearEval()
+        x = torch.randn(10, TOTAL_FEATURES, requires_grad=True)
+        y = model(x)
+        loss = y.sum()
+        loss.backward()
+        assert x.grad is not None
+
+
+if __name__ == "__main__":
+    pytest.main([__file__, "-v"])