Package CLI cleanup and PyPI tag publishing

[KiMiGuel]

Summary

• Add mexicosint.cli:run as the console entry point and support --number input.
• Remove the legacy bin/mexicosint shell launcher.
• Clean runtime dependencies and ignore local secrets/generated files.
• Update README, install, usage, config, and migration docs for the package workflow.
• Add .github/workflows/publish.yml to build and publish to PyPI on v* tags.

Validation

• Compared the previous package cleanup branch against main through the GitHub connector.
• Verified key branch files through the connector before opening this replacement PR.

Release setup needed

Before pushing a v* tag, add a repository secret named PYPI_API_TOKEN containing a PyPI API token.