Release 3.8.1.1: lighter idle UI poll, core cache, multicore ping.

Reduce idle CPU (cheap PollUI, binary cache, logbuf cap, DOM fingerprint),
speed ping/AWG HostPort, CopyBuffer pool; ship arm64 build and update notes.

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/protocols/awg/proxy.go

@@ -268,17 +268,24 @@ func handleHTTPProxy(client net.Conn, dial DialFunc) error {
 
 func relay(a, b net.Conn) error {
 	errc := make(chan error, 2)
-	go func() {
-		_, err := io.Copy(a, b)
+	copyOne := func(dst, src net.Conn) {
+		bufp := copyBufPool.Get().(*[]byte)
+		defer copyBufPool.Put(bufp)
+		_, err := io.CopyBuffer(dst, src, *bufp)
 		errc <- err
-	}()
-	go func() {
-		_, err := io.Copy(b, a)
-		errc <- err
-	}()
+	}
+	go copyOne(a, b)
+	go copyOne(b, a)
 	err := <-errc
 	_ = a.Close()
 	_ = b.Close()
 	<-errc
 	return err
 }
+
+var copyBufPool = sync.Pool{
+	New: func() any {
+		b := make([]byte, 32*1024)
+		return &b
+	},
+}