//! Agent tool extensions and unified registry.
//!
//! Extension sources:
//! - **builtin**: file ops, run_command, output, preview, chat (read_file, write_file, etc.)
//! - **memory**: memory_search, memory_write, memory_list (optional, enable_memory)
//! - **skills**: dynamically loaded from skill directories
//!
//! `ExtensionRegistry` provides a unified interface for tool discovery and execution.
pub use ;
pub use ;
pub use ;