Module reason 

Reason-layer enums and traits.

Enums

ConfErrReason

Configuration error sub-classification 配置错误子分类

ErrorCategory

Categorisation of an error for protocol-level routing and policy decisions.

UnifiedReason

Universal error reason classification with clear hierarchical structure 统一错误原因分类 - 采用清晰的分层结构

Traits

DomainReason

Marker trait for domain-specific error reason types.

ErrorCode

Legacy numeric error code.

ErrorIdentityProvider

Runtime identity provider for stable error codes and categories.