fix(proxy): preserve URL query/fragment and improve error handling

Extract shared URL utilities to handle query strings and fragments correctly.
Add race condition fix for URL preview, improve proxy toggle error feedback,
and support Codex chat format proxy endpoint.

src/components/providers/forms/shared/EndpointField.tsx

@@ -1,4 +1,4 @@
-import { useState, useEffect } from "react";
+import { useState, useEffect, useRef } from "react";
 import { useTranslation } from "react-i18next";
 import { FormLabel } from "@/components/ui/form";
 import { Input } from "@/components/ui/input";
@@ -40,6 +40,7 @@ export function EndpointField({
 }: EndpointFieldProps) {
   const { t } = useTranslation();
   const [urlPreview, setUrlPreview] = useState<UrlPreview | null>(null);
+  const lastRequestIdRef = useRef(0);
 
   const defaultManageLabel = t("providerForm.manageAndTest", {
     defaultValue: "管理和测速",
@@ -54,15 +55,18 @@ export function EndpointField({
 
     // 防抖：延迟 300ms 后请求
     const timer = setTimeout(async () => {
+      const requestId = ++lastRequestIdRef.current;
       try {
         const preview = await proxyApi.buildUrlPreview(
           appType,
           value,
           apiFormat,
         );
+        if (requestId !== lastRequestIdRef.current) return;
         setUrlPreview(preview);
       } catch (error) {
         console.error("Failed to build URL preview:", error);
+        if (requestId !== lastRequestIdRef.current) return;
         setUrlPreview(null);
       }
     }, 300);