pivot: replace WinDivert engine with embedded sing-box + wintun

After 5+ hours of WinDivert NETWORK-layer NAT-rewrite debugging
(streamdump pattern, SOCKET-layer SYN preemption, lazy PID resolution,
UDP ASSOCIATE relay + manual reinject), Discord voice still wouldn't
connect. The fundamental issue is that WinDivert reinjected UDP
packets don't always reach connect()-bound application sockets — the
demux happens at a layer above the reinject point.

dvp/force-proxy avoids this entirely via DLL injection (above the
kernel demux). We avoid it the other way: embed sing-box, let it run
TUN inbound + per-process routing rule + SOCKS5 outbound. TUN packets
are read by sing-box from kernel as a normal flow; the application
socket sees a normal flow back. No reinject hairpin, no SYN race, no
spoofing concerns.

What this commit does:
  - Drops internal/divert, internal/engine, internal/redirect,
    internal/socks5, internal/procscan, plus cmd/drover/{proxy,
    debugflow}_*.go subcommands (all WinDivert-only).
  - Adds internal/sboxrun — embed sing-box.exe (1.12.25) + wintun.dll
    (0.14.1) via //go:embed, install to %PROGRAMDATA%\Drover\sboxrun\
    with SHA256 verify, generate JSON config from form, spawn as
    subprocess, manage lifecycle.
  - Wires sboxrun into internal/gui/app.go: StartEngine/StopEngine
    now call sboxrun.Engine instead of windivert engine.
  - Fixes Wails binding: StartEngine(cfg) now passes the form config
    (was zero-arg, hit ProxyHost-required validation silently).

Manual test: Discord chat + voice work end-to-end through mihomo
upstream. Yandex Music / svchost / etc continue direct via
process_name routing rule.

Binary grew from 12 MB → 49 MB (37 MB sing-box embedded), but ships
fully self-contained. AV-friendly: wintun is Microsoft-signed, no
DLL injection.

WinDivert work preserved on experimental/windivert branch in case we
ever want to come back to that path.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/gui/app.go

@@ -12,7 +12,7 @@ import (
 	"time"
 
 	"git.okcu.io/root/drover-go/internal/checker"
-	"git.okcu.io/root/drover-go/internal/engine"
+	"git.okcu.io/root/drover-go/internal/sboxrun"
 	"github.com/wailsapp/wails/v2/pkg/runtime"
 )
 
@@ -28,7 +28,7 @@ type App struct {
 	version string
 
 	mu        sync.Mutex
-	eng       *engine.Engine
+	eng       *sboxrun.Engine
 	startedAt time.Time
 
 	// muCheck guards cancelCheck and checkDone.
@@ -179,24 +179,25 @@ func (a *App) StartEngine(cfg Config) error {
 	log.Printf("gui: StartEngine called host=%s port=%d auth=%v", cfg.Host, cfg.Port, cfg.Auth)
 	a.mu.Lock()
 	defer a.mu.Unlock()
-	if a.eng != nil && a.eng.Status() == engine.StatusActive {
+	if a.eng != nil && a.eng.Status() == sboxrun.StatusActive {
 		log.Printf("gui: StartEngine no-op (already active)")
 		return nil
 	}
-	e, err := engine.New(engine.Config{
-		ProxyAddr: fmt.Sprintf("%s:%d", cfg.Host, cfg.Port),
-		UseAuth:   cfg.Auth,
-		Login:     cfg.Login,
-		Password:  cfg.Password,
-		Targets:   []string{"Discord.exe", "DiscordCanary.exe", "DiscordPTB.exe", "Update.exe"},
+	e, err := sboxrun.New(sboxrun.Config{
+		ProxyHost:   cfg.Host,
+		ProxyPort:   cfg.Port,
+		UseAuth:     cfg.Auth,
+		Login:       cfg.Login,
+		Password:    cfg.Password,
+		TargetProcs: []string{"Discord.exe", "DiscordCanary.exe", "DiscordPTB.exe", "Update.exe"},
 	})
 	if err != nil {
-		log.Printf("gui: engine.New failed: %v", err)
+		log.Printf("gui: sboxrun.New failed: %v", err)
 		runtime.EventsEmit(a.ctx, "engine:status", map[string]any{"running": false, "error": err.Error()})
 		return err
 	}
 	if err := e.Start(a.ctx); err != nil {
-		log.Printf("gui: engine.Start failed: %v", err)
+		log.Printf("gui: sboxrun.Start failed: %v", err)
 		runtime.EventsEmit(a.ctx, "engine:status", map[string]any{"running": false, "error": err.Error()})
 		return err
 	}
@@ -224,7 +225,7 @@ func (a *App) StopEngine() error {
 func (a *App) GetStatus() map[string]any {
 	a.mu.Lock()
 	defer a.mu.Unlock()
-	running := a.eng != nil && a.eng.Status() == engine.StatusActive
+	running := a.eng != nil && a.eng.Status() == sboxrun.StatusActive
 	res := map[string]any{
 		"running": running,
 		"uptimeS": int(time.Since(a.startedAt).Seconds()),
@@ -247,7 +248,7 @@ func (a *App) statsLoop() {
 	defer tick.Stop()
 	for range tick.C {
 		a.mu.Lock()
-		if a.eng == nil || a.eng.Status() != engine.StatusActive || a.ctx == nil {
+		if a.eng == nil || a.eng.Status() != sboxrun.StatusActive || a.ctx == nil {
 			a.mu.Unlock()
 			continue
 		}