Modernize Public API Ergonomics

[tylerbutler]

The API is currently in a transitional state with mixed legacy and modern patterns.

Action Items:

• Deprecate makePolicy function formally (add @deprecated tag).
• Address ambiguous overloading in the policy() function (config vs options).
• Expose a public, programmatic checkRepository() API for use without the CLI.
• Clarify or improve excludeFiles behavior (currently regex strings, confusingly look like globs).