Add reset efficiency advice and friendly CLI

[aouxwoux]

Summary

• add a default-on efficiency recommendation showing when to use the next reset before expiry
• expose the recommendation in terminal, Markdown, and JSON output with a configurable buffer
• add a friendly codex_resets.py entry point with �ccount, estimate,
  ender, and help commands
• document the smoother command surface while keeping the lower-level scripts compatible

Tests

• python -m unittest discover -s tests
• python tools/validate_repo.py
• python tools/package_skill.py --dry-run

Note: commands were run with the bundled Codex Python runtime on this Windows machine.