refactor: Reorganize code structure and create tests directory

- Consolidate surrogates module to processors/surrogates/
- Move ensemble_surrogate.py to proper location
- Add deprecation shim for old import path
- Create tests/ directory with pytest structure
- Move test files from archive/test_scripts/
- Add conftest.py with shared fixtures

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/conftest.py

@@ -0,0 +1,32 @@
+"""
+Pytest configuration and shared fixtures for Atomizer tests.
+"""
+
+import pytest
+import sys
+from pathlib import Path
+
+# Add project root to path
+sys.path.insert(0, str(Path(__file__).parent.parent))
+
+@pytest.fixture
+def sample_study_dir(tmp_path):
+    """Create a temporary study directory structure."""
+    study = tmp_path / "test_study"
+    (study / "1_setup").mkdir(parents=True)
+    (study / "2_iterations").mkdir()
+    (study / "3_results").mkdir()
+    return study
+
+@pytest.fixture
+def sample_config():
+    """Sample optimization config for testing."""
+    return {
+        "study_name": "test_study",
+        "design_variables": [
+            {"name": "param1", "lower": 0, "upper": 10, "type": "continuous"}
+        ],
+        "objectives": [
+            {"name": "minimize_mass", "direction": "minimize"}
+        ]
+    }