fix: strip Claude Code attribution from non-Anthropic translations

internal/translator/codex/claude/codex_claude_request.go

@@ -12,6 +12,7 @@ import (
 	"strings"
 
 	"github.com/router-for-me/CLIProxyAPI/v7/internal/thinking"
+	"github.com/router-for-me/CLIProxyAPI/v7/internal/util"
 	"github.com/tidwall/gjson"
 	"github.com/tidwall/sjson"
 )
@@ -50,7 +51,7 @@ func ConvertClaudeRequestToCodex(modelName string, inputRawJSON []byte, _ bool)
 		contentIndex := 0
 
 		appendSystemText := func(text string) {
-			if text == "" || strings.HasPrefix(text, "x-anthropic-billing-header: ") {
+			if text == "" || util.IsClaudeCodeAttributionSystemText(text) {
 				return
 			}