Module unified_error 

Unified tool error envelope for consistent error handling across execution paths

This module consolidates error types from:

• handlers::ToolCallError
• handlers::ToolError
• middleware::MiddlewareError
• improvements_errors::ImprovementError
• Registry execution errors

By routing all errors through this envelope, we achieve:

• Consistent retry classification
• Uniform user-facing messaging
• Preserved debug context for diagnostics

Structs

DebugContext

Debug context for error diagnostics

UnifiedToolError

Unified tool error envelope

Enums

ErrorSeverity

Unified error severity levels

UnifiedErrorKind

Unified error kind for classification