Add comprehensive benchmark tests with quality validation

- Add conftest.py with 17 benchmark functions and known optima
- Add test_benchmarks.py with quality tolerance tests for all optimizer categories
- Add test_performance.py with regression baselines and critical path tests

Test improvements:
- Validate solutions against known optimal points (shifted_ackley at [1.0, 0.5])
- Flag solutions deviating from optimum as critical failures (distance > 0.2)
- Add xfail markers for optimizers prone to local minima on multimodal functions
- Include Himmelblau multi-optima handling
- Add reproducibility and bounds checking tests

356 test cases covering optimizer quality validation"

Author: renovate[bot]

.github/workflows/python-publish.yaml

@@ -69,7 +69,7 @@ jobs:
           name: python-package-distributions
           path: dist/
       - name: Sign the dists with Sigstore
-        uses: sigstore/gh-action-sigstore-python@v3.1.0
+        uses: sigstore/gh-action-sigstore-python@v3.2.0
         with:
           inputs: >-
             ./dist/*.tar.gz