docs(api): restore detailed docstrings in modular API

[dprada]

Summary

• restore the original rich docstrings for the modular introspection, extraction, comparison, conversion, construction, standardization, and validation helpers so the API documentation matches the pre-refactor content

Testing

• pytest

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https://chatgpt.com/codex/tasks/task_e_6909897b94e8832697b6e5e9171d9a90

[codecov]

Codecov Report

❌ Patch coverage is 77.42718% with 93 lines in your changes missing coverage. Please review.
✅ Project coverage is 73.92%. Comparing base (5a05733) to head (85a8ea3).
⚠️ Report is 17 commits behind head on main.
✅ All tests successful. No failed tests found.