API stability

The stability policy applies starting with fastauth 0.14.0. Stable contracts include documented exports and signatures, HTTP methods and schemas, documented storage/plugin protocols, configuration fields, and CLI commands.

A public removal requires a changelog entry, migration instructions, a FastAuthDeprecationWarning where possible, and at least one subsequent minor release before removal. Urgent pre-1.0 security fixes may bypass the window only when preserving behavior would leave users at risk.

The repository-root API_STABILITY.md is the authoritative policy.