Audit and tighten top-level public API exports (config + IO convenience aliases)

[Copilot]

• Investigate failing CI workflow/job logs for branch and identify root cause
• Apply minimal backward-compatible fix for Python 3.8 import regression introduced by top-level API exports
• Adjust focused tests to validate new behavior without eager-import side effects
• Run targeted tests reproducing the failing path and updated API export checks
• Run code review and security scan, then reply on PR comment with commit hash

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[SkBlaz]

@copilot tests fail

[Copilot]

@copilot tests fail

Fixed in commit dfaf0d6.

I traced the failing CI run (validate-quickstart (3.8)) to eager top-level py3plex.io imports added in py3plex/__init__.py, which triggered a Python 3.8 type-annotation evaluation error during import. I replaced those eager imports with lazy top-level wrapper aliases (save_to_arrow, load_from_arrow, save_network_to_parquet, load_network_from_parquet) so the API remains available without import-time regression.

Targeted tests were re-run after the change:

• python3 -m pytest tests/test_public_api_exports.py -q
• python3 -m pytest tests/test_config_api.py -q