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>

optimization_engine/surrogates/__init__.py

@@ -1,19 +1,26 @@
 """
-Surrogate models for FEA acceleration.
+DEPRECATED: This module has been moved to optimization_engine.processors.surrogates
 
-Available surrogates:
-- EnsembleSurrogate: Multiple MLPs with uncertainty quantification
-- OODDetector: Out-of-distribution detection
+Please update your imports:
+    from optimization_engine.processors.surrogates import EnsembleSurrogate
+
+This module will be removed in a future version.
 """
 
-from .ensemble_surrogate import (
+import warnings
+
+warnings.warn(
+    "optimization_engine.surrogates is deprecated. "
+    "Use optimization_engine.processors.surrogates instead.",
+    DeprecationWarning,
+    stacklevel=2
+)
+
+# Redirect imports
+from optimization_engine.processors.surrogates import (
     EnsembleSurrogate,
     OODDetector,
     create_and_train_ensemble
 )
 
-__all__ = [
-    'EnsembleSurrogate',
-    'OODDetector',
-    'create_and_train_ensemble'
-]
+__all__ = ['EnsembleSurrogate', 'OODDetector', 'create_and_train_ensemble']