Add CloseHandler to support graceful connection termination.

- Extend `test.proto` with `CloseCommand` and `CloseResponse` messages.
- Introduce `CloseHandler` to process "close" actions and respond with connection termination notice.
- Update `DelegateActionManager` to register `CloseHandler`.
- Refactor `IPCManager` to handle "close" response headers and terminate client connections gracefully.

src/main/proto/test.proto

@@ -21,4 +21,10 @@ message HeartbeatCommand {
 message HeartbeatResponse {
   int64 client_timestamp = 1;
   int64 server_timestamp = 2;
+}
+message CloseCommand {
+  // Vazio - apenas sinaliza fechamento
+}
+message CloseResponse {
+  string message = 1;
 }