v1.2.9: Comprehensive Integration Testing Suite (k8s & OOTB)

Release Notes
Integration Testing: Added robust end-to-end integration test suites (tests/k8s, tests/k8s_ootb, tests/ootb) covering Kubernetes sidecar behavior, concurrency memory limits, stream resilience, and out-of-the-box (OOTB) Docker standalone configurations.
Tooling Updates: Implemented run_stress_tests.sh and verification bash scripts (verify_k8s_ootb.sh, verify_ootb.sh) in the test harness for isolated automated smoke testing.
CI/CD Optimization: Fixed GitHub Actions pipeline failures by isolating local Kubernetes and Docker integration tests from standard unit test runs, ensuring green builds.
Code Quality: Resolved trailing whitespaces, unorganized imports, and E701 syntax linting errors via comprehensive ruff linting and formatting.
Benchmarking: Tracked exception and failure metrics during Locust load testing directly via CSV exports.
Docs: Migrated PyPI version badge to img.shields.io for instant cache invalidation.

Full Changelog: v1.2.7...v1.2.9