TUN inbound: Warn about forwarding on a new outbound interface too; Log failed restores of weak host send

As asked in review: switching between two interfaces with forwarding on now
warns about the new one, and an IPInterface failure while restoring weak
host send is logged, with the interface's name, instead of ignored.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

proxy/tun/tun_windows_outbound.go

@@ -27,6 +27,7 @@ type outboundGuard struct {
 	sync.Mutex
 	families   []winipcfg.AddressFamily
 	luid       winipcfg.LUID            // of the interface last checked
+	name       string                   // of that interface
 	turnedOff  []winipcfg.AddressFamily // where weak host send was turned off on it
 	forwarding bool                     // whether forwarding was on there
 	stopped    bool
@@ -48,10 +49,10 @@ func (g *outboundGuard) check() {
 	}
 	if luid != g.luid {
 		g.restoreLocked()
-		g.luid = luid
+		g.luid, g.name = luid, name
+		g.forwarding = false // to warn about the new interface as well
 	}
 	if luid == 0 {
-		g.forwarding = false
 		return
 	}
 	var forwarding []string
@@ -92,10 +93,12 @@ func (g *outboundGuard) restore() {
 
 func (g *outboundGuard) restoreLocked() {
 	for _, family := range g.turnedOff {
-		if row, err := g.luid.IPInterface(family); err == nil {
-			if err := setWeakHostSend(row, true); err != nil {
-				errors.LogWarningInner(context.Background(), err, "[tun] unable to turn weak host send on again for ", familyName(family))
-			}
+		row, err := g.luid.IPInterface(family)
+		if err == nil {
+			err = setWeakHostSend(row, true)
+		}
+		if err != nil {
+			errors.LogWarningInner(context.Background(), err, "[tun] unable to turn weak host send on again for ", familyName(family), " on ", g.name)
 		}
 	}
 	g.turnedOff = nil