v1.9.0

Added

• Private array backend (_array_backend) for pure Python array operations without NumPy
• Private math backend (_math_backend) for mathematical operations without SciPy
• Native DecisionTreeRegressor implementation
• Native ExtraTreesRegressor implementation
• Native RandomForestRegressor implementation
• Native GradientBoostingRegressor implementation
• SimpleProgressBar class as fallback when tqdm is unavailable
• Sigma self-adaptation for EvolutionStrategyOptimizer
• convergence_threshold parameter for Powell's Method
• Type hints to all optimizer classes and Search class
• Comprehensive docstrings for all optimizer classes
• Sphinx documentation with ReadTheDocs integration
• API tests for all optimizer categories

Changed

• scikit-learn is now an optional dependency (native estimators used by default)
• SciPy is now an optional dependency
• tqdm is now an optional dependency
• Complete reimplementation of Powell's Method with improved line search algorithms
• Reworked README with new 3D optimization animation
• Consolidated CI workflows into single ci.yml
• Restructured test directory (tests/test_main/, tests/test_internal/, etc.)
• Improved error messages with actionable suggestions

Removed

• BayesianRidge estimator
• Linear GP option from Gaussian Process regressor

Fixed

• Golden section search algorithm in Powell's Method
• Mutable default argument anti-pattern (constraints=[] changed to constraints=None)
• Missing @functools.wraps on internal decorators
• Division by zero edge case in print-times
• Bug in evaluate method