Complete public brief locale switching

frontend/components/landing/InstitutionalLandingPage.tsx

@@ -7,6 +7,7 @@ import {
 } from "@/components/landing/LandingAuthActions";
 import {
   LANDING_LOCALE_COOKIE,
+  landingLocaleHref,
   pickLandingLocale,
   type LandingLocale,
 } from "@/components/landing/landingLocale";
@@ -324,7 +325,7 @@ function InstitutionalLandingScreen({ locale }: { locale: LandingLocale }) {
             <Link href="/docs/chart-guide" className="hover:text-slate-950">
               {isEn ? "Guide" : "读图"}
             </Link>
-            <Link href="/briefs" className="hover:text-slate-950">
+            <Link href={landingLocaleHref("/briefs", locale)} className="hover:text-slate-950">
               {isEn ? "Briefs" : "简报"}
             </Link>
             <a href="#pricing" className="hover:text-slate-950">

frontend/components/landing/__tests__/landingPricingReferral.test.ts

@@ -104,7 +104,11 @@ export function runTests() {
     "landing supported cities must render names and station codes from the generated city groups",
   );
   assert(source.includes("#contact"), "landing navigation must expose the contact section");
-  assert(source.includes('href="/briefs"'), "landing navigation must expose public Weather Market Brief assets");
+  assert(
+    source.includes("landingLocaleHref") &&
+      source.includes('href={landingLocaleHref("/briefs", locale)}'),
+    "landing navigation must expose public Weather Market Brief assets while preserving the current locale",
+  );
   assert(source.includes('isEn ? "Briefs" : "简报"'), "landing page must label the public brief entry in both languages");
   assert(source.includes('id="contact"'), "landing page must include a contact section");
   assert(source.includes("yhrsc30@gmail.com"), "landing page must show the operator contact email");

frontend/components/landing/landingLocale.ts

@@ -38,3 +38,10 @@ export function pickLandingLocale(
 export function nextLandingLocale(locale: LandingLocale): LandingLocale {
   return locale === "zh-CN" ? "en-US" : "zh-CN";
 }
+
+export function landingLocaleHref(pathname: string, locale: LandingLocale): string {
+  const [pathWithQuery, hash] = pathname.split("#", 2);
+  const separator = pathWithQuery.includes("?") ? "&" : "?";
+  const localizedPath = `${pathWithQuery}${separator}${LANDING_LOCALE_QUERY_PARAM}=${encodeURIComponent(locale)}`;
+  return hash ? `${localizedPath}#${hash}` : localizedPath;
+}