feat: add iSH iPhone support and optimize slider captcha solver

Optimized slider captcha solver to avoid CPU/RAM-heavy image rendering.
Added legacy TCP accept support specifically for iSH on linux/386 arch.
Fixed 'accept4: function not implemented' error in VLESS mode on iSH.

client/ish_listener_linux_386.go

@@ -0,0 +1,74 @@
+//go:build linux && 386
+package main
+
+import (
+	"net"
+	"os"
+	"syscall"
+	"time"
+	"unsafe"
+)
+
+type ishListener struct {
+	net.Listener
+	fd int
+}
+
+// wrapISHListener overrides the standard net.Listener with a legacy syscall listener
+// designed specifically for the iSH simulator on iOS, which lacks modern `accept4`.
+func wrapISHListener(ln net.Listener) (net.Listener, error) {
+	tl, ok := ln.(*net.TCPListener)
+	if !ok {
+		return ln, nil
+	}
+	f, err := tl.File()
+	if err != nil {
+		return nil, err
+	}
+	
+	return &ishListener{Listener: ln, fd: int(f.Fd())}, nil
+}
+
+func (l *ishListener) Accept() (net.Conn, error) {
+	for {
+		addr := make([]byte, 128)
+		addrlen := uintptr(128)
+		
+		// i386 network syscalls are multiplexed via socketcall (102). 
+		// SYS_ACCEPT is subcall 5.
+		args := [3]uintptr{uintptr(l.fd), uintptr(unsafe.Pointer(&addr[0])), uintptr(unsafe.Pointer(&addrlen))}
+		
+		r1, _, errno := syscall.Syscall(102, 5, uintptr(unsafe.Pointer(&args)), 0)
+		if errno != 0 {
+			if errno == syscall.EAGAIN || errno == syscall.EINTR || errno == syscall.EWOULDBLOCK {
+				time.Sleep(50 * time.Millisecond) // Just in case it's non-blocking somehow
+				continue
+			}
+			return nil, errno
+		}
+		
+		nfd := int(r1)
+		
+		// Wrap raw FD into os.File, then into a net.Conn.
+		// fileConn duplicates the fd again.
+		f := os.NewFile(uintptr(nfd), "ish-conn")
+		conn, err := net.FileConn(f)
+		f.Close()
+		
+		if err != nil {
+			syscall.Close(nfd)
+			return nil, err
+		}
+		
+		return conn, nil
+	}
+}
+
+func (l *ishListener) Close() error {
+	err1 := syscall.Close(l.fd)
+	err2 := l.Listener.Close()
+	if err1 != nil {
+		return err1
+	}
+	return err2
+}

client/ish_listener_other.go

@@ -0,0 +1,9 @@
+//go:build !(linux && 386)
+package main
+
+import "net"
+
+// wrapISHListener is a no-op for architectures that don't need the legacy socketcall accept bypass.
+func wrapISHListener(ln net.Listener) (net.Listener, error) {
+	return ln, nil
+}

client/main.go

@@ -2036,12 +2036,19 @@ func runVLESSMode(ctx context.Context, tp *turnParams, peer *net.UDPAddr, listen
 	if err != nil {
 		log.Panicf("TCP listen: %s", err)
 	}
-	context.AfterFunc(ctx, func() { _ = listener.Close() })
+	
+	wrappedListener, err := wrapISHListener(listener)
+	if err != nil {
+		log.Printf("Warning: failed to wrap listener: %v", err)
+		wrappedListener = listener
+	}
+	
+	context.AfterFunc(ctx, func() { _ = wrappedListener.Close() })
 	log.Printf("VLESS mode: listening on %s (round-robin across %d sessions)", listenAddr, numSessions)
 
 	var wgConn sync.WaitGroup
 	for {
-		tcpConn, err := listener.Accept()
+		tcpConn, err := wrappedListener.Accept()
 		if err != nil {
 			select {
 			case <-ctx.Done():

client/slider_captcha.go

@@ -715,12 +715,70 @@ func rankSliderCandidates(img image.Image, gridSize int, swaps []int) ([]sliderC
 }
 
 func scoreSliderCandidate(img image.Image, gridSize int, mapping []int) (int64, error) {
-	rendered, err := renderSliderCandidate(img, gridSize, mapping)
-	if err != nil {
-		return 0, err
+	bounds := img.Bounds()
+	var score int64
+
+	for row := 0; row < gridSize; row++ {
+		for col := 0; col < gridSize-1; col++ {
+			dstLeftIndex := row*gridSize + col
+			dstRightIndex := row*gridSize + col + 1
+			srcLeftIndex := mapping[dstLeftIndex]
+			srcRightIndex := mapping[dstRightIndex]
+
+			dstLeftRect := sliderTileRect(bounds, gridSize, dstLeftIndex)
+			dstRightRect := sliderTileRect(bounds, gridSize, dstRightIndex)
+			srcLeftRect := sliderTileRect(bounds, gridSize, srcLeftIndex)
+			srcRightRect := sliderTileRect(bounds, gridSize, srcRightIndex)
+
+			height := minInt(dstLeftRect.Dy(), dstRightRect.Dy())
+
+			leftSrcXRel := (dstLeftRect.Dx() - 1) * srcLeftRect.Dx() / dstLeftRect.Dx()
+			sxLeft := srcLeftRect.Min.X + leftSrcXRel
+			sxRight := srcRightRect.Min.X
+
+			for offset := 0; offset < height; offset++ {
+				syLeft := srcLeftRect.Min.Y + offset*srcLeftRect.Dy()/dstLeftRect.Dy()
+				syRight := srcRightRect.Min.Y + offset*srcRightRect.Dy()/dstRightRect.Dy()
+
+				score += pixelDiff(
+					img.At(sxLeft, syLeft),
+					img.At(sxRight, syRight),
+				)
+			}
+		}
+	}
+
+	for row := 0; row < gridSize-1; row++ {
+		for col := 0; col < gridSize; col++ {
+			dstTopIndex := row*gridSize + col
+			dstBottomIndex := (row+1)*gridSize + col
+			srcTopIndex := mapping[dstTopIndex]
+			srcBottomIndex := mapping[dstBottomIndex]
+
+			dstTopRect := sliderTileRect(bounds, gridSize, dstTopIndex)
+			dstBottomRect := sliderTileRect(bounds, gridSize, dstBottomIndex)
+			srcTopRect := sliderTileRect(bounds, gridSize, srcTopIndex)
+			srcBottomRect := sliderTileRect(bounds, gridSize, srcBottomIndex)
+
+			width := minInt(dstTopRect.Dx(), dstBottomRect.Dx())
+
+			topSrcYRel := (dstTopRect.Dy() - 1) * srcTopRect.Dy() / dstTopRect.Dy()
+			syTop := srcTopRect.Min.Y + topSrcYRel
+			syBottom := srcBottomRect.Min.Y
+
+			for offset := 0; offset < width; offset++ {
+				sxTop := srcTopRect.Min.X + offset*srcTopRect.Dx()/dstTopRect.Dx()
+				sxBottom := srcBottomRect.Min.X + offset*srcBottomRect.Dx()/dstBottomRect.Dx()
+
+				score += pixelDiff(
+					img.At(sxTop, syTop),
+					img.At(sxBottom, syBottom),
+				)
+			}
+		}
 	}
 
-	return scoreRenderedSliderImage(rendered, gridSize), nil
+	return score, nil
 }
 
 func renderSliderCandidate(img image.Image, gridSize int, mapping []int) (*image.RGBA, error) {
@@ -744,40 +802,6 @@ func renderSliderCandidate(img image.Image, gridSize int, mapping []int) (*image
 	return rendered, nil
 }
 
-func scoreRenderedSliderImage(img image.Image, gridSize int) int64 {
-	bounds := img.Bounds()
-	var score int64
-
-	for row := 0; row < gridSize; row++ {
-		for col := 0; col < gridSize-1; col++ {
-			leftRect := sliderTileRect(bounds, gridSize, row*gridSize+col)
-			rightRect := sliderTileRect(bounds, gridSize, row*gridSize+col+1)
-			height := minInt(leftRect.Dy(), rightRect.Dy())
-			for offset := 0; offset < height; offset++ {
-				score += pixelDiff(
-					img.At(leftRect.Max.X-1, leftRect.Min.Y+offset),
-					img.At(rightRect.Min.X, rightRect.Min.Y+offset),
-				)
-			}
-		}
-	}
-
-	for row := 0; row < gridSize-1; row++ {
-		for col := 0; col < gridSize; col++ {
-			topRect := sliderTileRect(bounds, gridSize, row*gridSize+col)
-			bottomRect := sliderTileRect(bounds, gridSize, (row+1)*gridSize+col)
-			width := minInt(topRect.Dx(), bottomRect.Dx())
-			for offset := 0; offset < width; offset++ {
-				score += pixelDiff(
-					img.At(topRect.Min.X+offset, topRect.Max.Y-1),
-					img.At(bottomRect.Min.X+offset, bottomRect.Min.Y),
-				)
-			}
-		}
-	}
-
-	return score
-}
 
 func sliderTileRect(bounds image.Rectangle, gridSize int, index int) image.Rectangle {
 	row := index / gridSize