fix(rpc): stop server before joining threads in crpc_deinit

crpc_deinit() called TcpServer::join() without stop(), so with any live
TCP client the accept thread never exited and deinit blocked forever on
the caller's thread (froze the Unity main thread in OnDestroy during
e2e). Call server->stop() first, which clears running_ and unblocks
accept, then join.

src/server_api.cpp

@@ -98,8 +98,13 @@ void crpc_init_with_address(const char *ip, int port) {
 }
 
 void crpc_deinit() {
-    if (server)
+    if (server) {
+        // Must stop() before join(): stop() clears running_ so the accept
+        // thread can exit; join() alone would block forever while a client
+        // thread is blocked in a read (deadlock observed in Unity e2e).
+        server->stop();
         server->join();
+    }
     server.reset();
     std::lock_guard lock(gc_mtx);
     gc.clear();