API Design Principles

• Public APIs are defined by interfaces in foundation, core, and each domain package's top-level __init__.py.
• Prefer keyword-only arguments for anything beyond the first positional parameter.
• Every public class documents Purpose, Responsibility, Dependencies.
• Favor small Protocols/ABCs over large "god objects".
• Backward compatibility is preserved within a MAJOR version wherever possible (see versioning-policy.md).