fix: 修复连接状态下切换配置后断开重连导致异常的问题

问题现象：连接中切换配置 -> 断开 -> 连接，会出现连接后瞬间断开、
长时间无法重连。而先断开再切换配置则正常。

根因分析（三个层面的资源泄漏叠加）：

1. pumpPackets 死锁 (session.go)
   Disconnect() 只关闭 WebSocket transport，不关闭 TUN 设备。
   TUN->WS goroutine 阻塞在 dev.Read()，pumpPackets 的 wg.Wait()
   永远不返回，cleanup()（关闭 TUN/删路由）无法执行，导致
   TUN 设备和路由泄漏。

2. 僵尸 eventLoop + 僵尸 IPC 连接 (view.go)
   onDisconnect 不清空 ipcClient、不关闭 IPC 连接，旧 eventLoop
   持续运行接收广播事件。eventLoop 正常事件处理无身份校验，
   旧 session 的 disconnected 广播会覆盖新 session 的 connected 状态。

3. stopSession 不等待 goroutine 退出 (daemon.go)
   d.session = nil 在 goroutine 仍在运行时即设置，新旧 session
   并发执行导致 TUN/路由冲突。无 mutex 保护并发访问。

修复内容（10 项，3 个文件）：

session.go:
- Disconnect() 新增 dev.Close() 解除 pumpPackets 死锁
- 新增 done channel，Disconnect() 阻塞等待 run goroutine 完全退出
- run() deferred setState 跳过用户主动断开时的冗余广播
- run() 顶部 ctx.Err() 检查后补 cleanup()

daemon.go:
- 新增 sync.Mutex 保护 session/cancel 并发访问
- 拆分 stopSession/stopSessionLocked 避免死锁

view.go:
- onDisconnect 置 ipcClient=nil + client.Close() 终止僵尸 eventLoop
- eventLoop 三个事件分支均加 if current == client 身份校验
- onConnect 覆盖前清理旧 IPC client
- setConnButtons 连接时禁用配置下拉框

Makefile

@@ -11,7 +11,7 @@ GO          = go
 CGO_ENABLED = 1
 WINDRES     ?= x86_64-w64-mingw32-windres
 MINGW_CC    ?= x86_64-w64-mingw32-gcc
-SEMVER      ?= 0.4.1
+SEMVER      ?= 0.4.2
 GIT_HASH    = $(shell git rev-parse --short HEAD 2>/dev/null || echo unknown)
 VERSION     = $(SEMVER)-$(GIT_HASH)
 LDFLAGS     = -s -w -X lmvpn/internal/version.Version=$(VERSION)

internal/daemon/daemon.go

@@ -19,6 +19,7 @@ import (
 	"net"
 	"os"
 	"os/signal"
+	"sync"
 	"syscall"
 
 	"lmvpn/internal/ipc"
@@ -92,6 +93,7 @@ func chownToUser(path string, uid, gid int) {
 
 type daemon struct {
 	server  *ipc.Server
+	mu      sync.Mutex
 	session *vpn.SessionManager
 	cancel  context.CancelFunc
 }
@@ -109,8 +111,11 @@ func (d *daemon) handle(conn net.Conn, req ipc.Request) {
 		d.server.Close()
 		os.Exit(0)
 	case ipc.CmdStats:
-		if d.session != nil {
-			snap := d.session.Stats().Snapshot()
+		d.mu.Lock()
+		sess := d.session
+		d.mu.Unlock()
+		if sess != nil {
+			snap := sess.Stats().Snapshot()
 			d.server.Broadcast(ipc.Event{Event: ipc.EvStats, Stats: &snap})
 		}
 		_ = ipc.WriteOK(conn)
@@ -122,12 +127,14 @@ func (d *daemon) handle(conn net.Conn, req ipc.Request) {
 }
 
 func (d *daemon) startSession(conn net.Conn, req ipc.Request) {
+	d.mu.Lock()
+	defer d.mu.Unlock()
 	if req.Config == nil {
 		_ = ipc.WriteErr(conn, "missing config")
 		return
 	}
 	if d.session != nil {
-		d.stopSession()
+		d.stopSessionLocked()
 	}
 
 	cfg := vpn.SessionConfig{
@@ -170,6 +177,12 @@ func (d *daemon) startSession(conn net.Conn, req ipc.Request) {
 }
 
 func (d *daemon) stopSession() {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+	d.stopSessionLocked()
+}
+
+func (d *daemon) stopSessionLocked() {
 	if d.cancel != nil {
 		d.cancel()
 		d.cancel = nil

internal/ui/view.go

@@ -39,6 +39,13 @@ func (a *App) setConnButtons(connectEnabled, disconnectEnabled bool) {
 	} else {
 		a.disconnectBtn.Disable()
 	}
+	if a.profileSelect != nil {
+		if connectEnabled {
+			a.profileSelect.Enable()
+		} else {
+			a.profileSelect.Disable()
+		}
+	}
 	a.setupTray()
 }
 
@@ -132,8 +139,13 @@ func (a *App) onConnect() {
 		}
 
 		a.mu.Lock()
+		oldClient := a.ipcClient
 		a.ipcClient = client
 		a.mu.Unlock()
+		if oldClient != nil {
+			_ = ipc.SendStop(oldClient)
+			oldClient.Close()
+		}
 
 		// Get password from keychain.
 		password, err := a.kc.GetPassword(a.currentProfile.Name)
@@ -190,13 +202,24 @@ func (a *App) onConnect() {
 func (a *App) onDisconnect() {
 	a.mu.Lock()
 	client := a.ipcClient
+	a.ipcClient = nil
 	a.mu.Unlock()
 	if client == nil {
 		return
 	}
 	_ = ipc.SendStop(client)
+	client.Close()
 	a.setConnButtons(true, false)
 	a.stateLabel.SetText(i18n.T("StateDisconnected"))
+	a.ipLabel.SetText(i18n.T("IpNone"))
+	a.ip6Label.SetText(i18n.T("Ip6None"))
+	a.uptimeLabel.SetText(i18n.T("UptimeNone"))
+	a.rxV4Label.SetText(i18n.T("RxV4Zero"))
+	a.txV4Label.SetText(i18n.T("TxV4Zero"))
+	a.rxV6Label.SetText(i18n.T("RxV6Zero"))
+	a.txV6Label.SetText(i18n.T("TxV6Zero"))
+	a.rxTotalLabel.SetText(i18n.T("RxTotalZero"))
+	a.txTotalLabel.SetText(i18n.T("TxTotalZero"))
 }
 
 // eventLoop reads IPC events from the daemon and updates the UI.
@@ -234,17 +257,33 @@ func (a *App) eventLoop() {
 		switch ev.Event {
 		case ipc.EvState:
 			fyne.Do(func() {
-				a.applyState(ev.State)
+				a.mu.Lock()
+				current := a.ipcClient
+				a.mu.Unlock()
+				if current == client {
+					a.applyState(ev.State)
+				}
 			})
 		case ipc.EvStats:
 			if ev.Stats != nil {
 				s := *ev.Stats
 				fyne.Do(func() {
-					a.applyStats(s)
+					a.mu.Lock()
+					current := a.ipcClient
+					a.mu.Unlock()
+					if current == client {
+						a.applyStats(s)
+					}
 				})
 			}
 		case ipc.EvError:
 			fyne.Do(func() {
+				a.mu.Lock()
+				current := a.ipcClient
+				a.mu.Unlock()
+				if current != client {
+					return
+				}
 				if ev.Code == "tls_error" {
 					showError(i18n.T("DlgTLSError"),
 						i18n.T("TLSErrorVerification")+"\n\n"+ev.Message, a.window)

internal/vpn/session.go

@@ -60,6 +60,7 @@ type SessionManager struct {
 	dev      tun.Device
 	routeMgr *route.Manager
 	conn     *transport.Conn
+	done     chan struct{}
 
 	// EWMA speed smoothing state. Only touched by reportStats (single
 	// goroutine), so no lock needed. ewma* fields hold the smoothed
@@ -106,6 +107,7 @@ func (sm *SessionManager) Connect(ctx context.Context, cfg SessionConfig) error
 	ctx, cancel := context.WithCancel(ctx)
 	sm.cancel = cancel
 	sm.running = true
+	sm.done = make(chan struct{})
 	sm.mu.Unlock()
 
 	go sm.run(ctx, cfg)
@@ -126,21 +128,32 @@ func (sm *SessionManager) Disconnect() {
 	if cancel != nil {
 		cancel()
 	}
-	// Close the transport to unblock the packet pump.
+	// Close the transport to unblock the WS->TUN goroutine.
 	sm.mu.Lock()
 	conn := sm.conn
+	dev := sm.dev
 	sm.mu.Unlock()
 	if conn != nil {
 		conn.Close()
 	}
+	// Close the TUN device to unblock the TUN->WS goroutine's dev.Read().
+	if dev != nil {
+		dev.Close()
+	}
+	// Wait for the run goroutine to fully exit so that cleanup
+	// (route removal, TUN teardown) is complete before returning.
+	if sm.done != nil {
+		<-sm.done
+	}
 }
 
 // run is the main session loop with exponential-backoff reconnection
 // and CDN IP failover.
 func (sm *SessionManager) run(ctx context.Context, cfg SessionConfig) {
 	fatal := false
+	defer close(sm.done)
 	defer func() {
-		if !fatal {
+		if !fatal && ctx.Err() == nil {
 			sm.setState(stats.StateDisconnected)
 		}
 	}()
@@ -154,6 +167,7 @@ func (sm *SessionManager) run(ctx context.Context, cfg SessionConfig) {
 
 	for {
 		if ctx.Err() != nil {
+			sm.cleanup()
 			return
 		}