feat(host): complete launcher and gateway multi-host binding support

- add shared netbind planning for strict tcp4/tcp6 bind semantics
- support launcher/gateway host env overrides and launcher-to-gateway forwarding
- cover host binding and forwarding with network and subprocess env tests

cmd/picoclaw/internal/gateway/command.go

@@ -3,7 +3,6 @@ package gateway
 import (
 	"fmt"
 	"os"
-	"strings"
 
 	"github.com/spf13/cobra"
 
@@ -11,15 +10,19 @@ import (
 	"github.com/sipeed/picoclaw/pkg/config"
 	"github.com/sipeed/picoclaw/pkg/gateway"
 	"github.com/sipeed/picoclaw/pkg/logger"
+	"github.com/sipeed/picoclaw/pkg/netbind"
 	"github.com/sipeed/picoclaw/pkg/utils"
 )
 
 func resolveGatewayHostOverride(explicit bool, host string) (string, error) {
-	host = strings.TrimSpace(host)
-	if explicit && host == "" {
-		return "", fmt.Errorf("the --host option cannot be empty")
+	if !explicit {
+		return "", nil
 	}
-	return host, nil
+	normalized, err := netbind.NormalizeHostInput(host)
+	if err != nil {
+		return "", fmt.Errorf("invalid --host value: %w", err)
+	}
+	return normalized, nil
 }
 
 func NewGatewayCommand() *cobra.Command {

cmd/picoclaw/internal/gateway/command_test.go

@@ -43,6 +43,7 @@ func TestResolveGatewayHostOverride(t *testing.T) {
 		{name: "implicit empty host is allowed", explicit: false, host: "", wantHost: "", wantErr: false},
 		{name: "explicit empty host rejected", explicit: true, host: "   ", wantHost: "", wantErr: true},
 		{name: "explicit localhost kept", explicit: true, host: " localhost ", wantHost: "localhost", wantErr: false},
+		{name: "explicit multi host normalized", explicit: true, host: " [::1] , 127.0.0.1 ", wantHost: "::1,127.0.0.1", wantErr: false},
 	}
 
 	for _, tt := range tests {