Fix missing unistd.h in discovery_cli (pause declaration)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

dev/cli/discovery_cli.c

@@ -1,6 +1,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 #include <arpa/inet.h>
 
 #include "discovery.h"