docs: Add comprehensive manual testing script

28 manual test cases covering:
- Core service functionality (Pattern Learning, LLM Chat, Cost Estimator)
- UI workflow buttons (Code Review, doc-gen, release-prep, secure-release)
- Error handling & resilience
- Configuration & settings
- Context building & detection
- Integration tests (end-to-end workflows)
- Performance & limits
- Documentation & accessibility
- Regression tests

Designed for QA testing that cannot be automated programmatically.

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Co-Authored-By: Claude Sonnet 4.5 <[email protected]>

Author: 2 people