fix(sub): pass numeric XMUX counts to Clash reuse-settings (#6843)

Inbound XMUX counts such as maxConnections are stored as JSON numbers, but
buildXhttpClashOpts kept only string values, so the panel default
maxConnections: 3 never reached Clash/Mihomo clients. Numeric values are now
rendered as plain integers (FormatFloat, so 1000000 does not become 1e+06) and
zero values are still dropped.

internal/sub/clash_service.go

@@ -1018,8 +1018,15 @@ func buildXhttpClashOpts(xhttp map[string]any) map[string]any {
 			{"hMaxRequestTimes", "h-max-request-times"},
 			{"hMaxReusableSecs", "h-max-reusable-secs"},
 		} {
-			if v, ok := xmux[f.src].(string); ok && v != "" {
-				reuse[f.dst] = v
+			v, ok := nonZeroShareValue(xmux[f.src])
+			if !ok {
+				continue
+			}
+			if n, isFloat := v.(float64); isFloat {
+				// JSON numbers decode as float64, and %v would render 1000000 as "1e+06".
+				reuse[f.dst] = strconv.FormatFloat(n, 'f', -1, 64)
+			} else {
+				reuse[f.dst] = fmt.Sprint(v)
 			}
 		}
 		if v, ok := nonZeroShareValue(xmux["hKeepAlivePeriod"]); ok {

internal/sub/clash_service_test.go

@@ -1,6 +1,7 @@
 package sub
 
 import (
+	"encoding/json"
 	"fmt"
 	"reflect"
 	"testing"
@@ -798,6 +799,37 @@ func TestBuildXhttpClashOpts_XmuxMapsToReuseSettings(t *testing.T) {
 			t.Error("reuse-settings should not appear when only hKeepAlivePeriod=0")
 		}
 	})
+
+	// Sub-test 5: numeric counts as json.Unmarshal yields them (#6841)
+	t.Run("NumericXmux", func(t *testing.T) {
+		cases := []struct {
+			name, xmux string
+			want       map[string]any
+		}{
+			{
+				name: "PanelDefaults",
+				xmux: `{"maxConcurrency":"","maxConnections":3,"cMaxReuseTimes":0,"hMaxRequestTimes":"600-900","hMaxReusableSecs":"1800-3000","hKeepAlivePeriod":0}`,
+				want: map[string]any{"max-connections": "3", "h-max-request-times": "600-900", "h-max-reusable-secs": "1800-3000"},
+			},
+			{
+				name: "LargeCountNotExponent",
+				xmux: `{"cMaxReuseTimes":1000000}`,
+				want: map[string]any{"c-max-reuse-times": "1000000"},
+			},
+		}
+		for _, tc := range cases {
+			t.Run(tc.name, func(t *testing.T) {
+				var xmux map[string]any
+				if err := json.Unmarshal([]byte(tc.xmux), &xmux); err != nil {
+					t.Fatal(err)
+				}
+				opts := buildXhttpClashOpts(map[string]any{"path": "/", "xmux": xmux})
+				if got := opts["reuse-settings"]; !reflect.DeepEqual(got, tc.want) {
+					t.Errorf("reuse-settings = %#v, want %#v", got, tc.want)
+				}
+			})
+		}
+	})
 }
 
 func TestBuildXhttpClashOpts_ServerOnlyFieldsExcluded(t *testing.T) {