添加协议层数据统计结构，日志文件保存在 Logs 下

openspec/specs/kcp-transport/spec.md

@@ -1,4 +1,4 @@
-# kcp-transport Specification
+# kcp-transport Specification
 
 ## Purpose
 TBD - created by archiving change introduce-kcp-transport. Update Purpose after archive.
@@ -61,3 +61,15 @@ The codebase SHALL NOT keep a directly instantiable `ReliableUdpTransport` entry
 - **WHEN** developers inspect the transport implementations available to runtime code
 - **THEN** they do not find a usable `ReliableUdpTransport` class representing reliable delivery
 - **THEN** the remaining transport naming makes the reliable-versus-unreliable boundary explicit
+### Requirement: KCP transport can emit structured metrics through an optional module
+`KcpTransport` SHALL allow callers to provide an optional transport metrics module without changing the shared `ITransport` contract. While running, `KcpTransport` MUST publish transport lifecycle, session creation and disposal, logical payload traffic, UDP datagram traffic, and transport-stage errors into that module, and it MUST expose a current metrics snapshot query for diagnostics and tests.
+
+#### Scenario: Injected metrics module receives KCP traffic statistics
+- **WHEN** a caller starts a `KcpTransport`, sends and receives payloads, and then stops the transport
+- **THEN** the injected metrics module receives enough events to aggregate the run's payload, datagram, session, and error statistics
+- **THEN** diagnostics code can query the current snapshot without reading the exported report file
+
+#### Scenario: Default metrics module exports on KCP transport shutdown
+- **WHEN** a caller uses `KcpTransport` without providing a custom metrics module and later calls `Stop()`
+- **THEN** the transport uses its built-in metrics module to finalize the run summary during shutdown
+- **THEN** the transport emits the final JSON report and compact console summary exactly once for that run