Release v3.19.19

Release v3.19.19 - TDD Book 100% Validation + CI/CD Integration

🎉 Major Milestone Release

Highlights:
- ✅ 100% TDD Book Validation: 27/27 stdlib modules, 151/151 tests passing
- 🔧 CI/CD Integration: Continuous regression protection for validated stdlib
- 🐛 4 Critical Bugs Fixed: DEPYLER-0021, 0022, 0023 (+ regression), 0024
- 📚 Comprehensive Documentation: README stdlib support matrix
- 🎯 Production Ready: Validated stdlib subset safe for production use

Validated Stdlib Modules (27):
- Data Serialization: json, struct, base64, csv
- Date/Time: datetime, calendar, time
- Cryptography: hashlib, secrets
- Text Processing: textwrap, re, string
- Memory/Data: copy, memoryview, array
- Math/Numeric: math, decimal, fractions, statistics
- Functional: itertools, functools
- File System: os, pathlib, io
- Data Structures: collections
- Random: random, secrets
- System: sys

Quality Metrics:
- Tests: 151/151 TDD Book tests passing (100%)
- Bug Discovery: 4 critical bugs found and fixed (100% resolution rate)
- CI/CD: Continuous validation on every PR/push
- Production Status: Safe for production use with validated modules

See CHANGELOG.md for complete details.