Fix unix sockets issue on FreeBSD

Sometimes a unix socket has a 0 status return which indicates the connection
immediately succeeded, at which point entering the event loop waiting on the
connection to complete actually breaks things.

It seems on FreeBSD with events being edge triggered, we're awaiting a
connection to signal it's writeable (to complete the connection) but that
never occurs (the event already took place before we registered for the
event). Going by status alone to determine if we should enter into the event
loop to await the complete connection seems sensible here.

src/core/net.c

@@ -572,7 +572,15 @@ JANET_CORE_FN(cfun_net_connect,
     }
 #endif
 
-    if (status) {
+    if (status == 0) {
+        /* Connect completed synchronously (common for unix domain sockets).
+         * Return the stream directly without scheduling an async wait,
+         * as edge-triggered kqueue may not signal EVFILT_WRITE if the socket
+         * is already connected when registered. */
+        return janet_wrap_abstract(stream);
+    }
+
+    if (status == -1) {
 #ifdef JANET_WINDOWS
         if (err != WSAEWOULDBLOCK) {
 #else