refactor: split protocol endpoint into focused modules

src/protocol/tree/endpoint/mod.rs

@@ -0,0 +1,22 @@
+//! Endpoint runtime and traits.
+//!
+//! This module provides the core logic for a protocol endpoint, including
+//! packet ingress, routing decisions, and hook lifecycle management.
+//!
+//! Protocol section mapping:
+//! - `builders`: packet construction and outbound hook declaration
+//! - `receive`: framed ingress, authority checks, and route selection
+//! - `hooks`: hook lifecycle, peer validation, and fault emission
+//! - `introspection`: reserved empty-procedure discovery responses
+//! - `core`: externally visible endpoint state and result types
+
+mod builders;
+mod core;
+mod hooks;
+mod introspection;
+mod receive;
+
+pub use core::{
+    ChildRoute, ConnectionState, Endpoint, EndpointError, EndpointOutcome, Ingress,
+    LeafBehavior, LeafSpec, LocalEvent, ProtocolEndpoint,
+};