Fix hub iframe nav flicker with normal navigation and loading overlay

Co-authored-by: Cursor <cursoragent@cursor.com>

static/instance_theme.js

@@ -329,41 +329,33 @@
     }
   }
 
-  /** 仅中控 iframe 内：fetch + document.write 换页，避免 iframe 整页卸载白屏。单独打开实例仍走浏览器正常跳转。 */
+  function notifyParentFrameNavStart() {
+    if (!isHubLinked()) return;
+    try {
+      window.parent.postMessage({ type: "instance-frame-navigating", theme: get() }, "*");
+    } catch (_) {}
+  }
+
+  function notifyParentFrameReady() {
+    if (!isHubLinked()) return;
+    try {
+      window.parent.postMessage({ type: "instance-frame-ready", theme: get() }, "*");
+    } catch (_) {}
+  }
+
+  /** 中控 iframe：顶栏用正常跳转（与单独打开实例一致），由中控 shell 遮罩盖住 iframe 加载过程。 */
   function initHubEmbedInFrameNav() {
     if (!isHubLinked()) return;
 
-    let navToken = 0;
-
     function isSoftNavLink(a) {
       if (!a || !a.getAttribute) return false;
+      if (a.hasAttribute("download") || a.target === "_blank") return false;
       return !!a.closest(".top-nav, .strategy-subnav");
     }
 
-    async function navigateInFrame(href, opts) {
-      const token = ++navToken;
-      try {
-        const r = await fetch(href, { credentials: "same-origin" });
-        if (token !== navToken) return;
-        if (!r.ok) {
-          location.href = href;
-          return;
-        }
-        const html = await r.text();
-        if (token !== navToken) return;
-        let path = href;
-        try {
-          const u = new URL(href, location.href);
-          path = u.pathname + u.search + u.hash;
-        } catch (_) {}
-        if (opts && opts.replace) history.replaceState(null, "", path);
-        else history.pushState(null, "", path);
-        document.open();
-        document.write(html);
-        document.close();
-      } catch (_) {
-        if (token === navToken) location.href = href;
-      }
+    function navigateTopNav(href) {
+      notifyParentFrameNavStart();
+      location.assign(href);
     }
 
     document.addEventListener(
@@ -384,14 +376,12 @@
         const nextHref = target.pathname + target.search + target.hash;
         if (target.pathname === location.pathname && target.search === location.search) return;
         ev.preventDefault();
-        void navigateInFrame(nextHref);
+        navigateTopNav(nextHref);
       },
       true
     );
 
-    window.addEventListener("popstate", () => {
-      void navigateInFrame(location.pathname + location.search + location.hash, { replace: true });
-    });
+    window.addEventListener("pagehide", notifyParentFrameNavStart);
   }
 
   function purgeLegacySoftNavCache() {
@@ -418,6 +408,7 @@
       apply(get(), { skipStore: true });
       window.addEventListener("message", (ev) => initFromHubMessage(ev.data));
       initHubEmbedInFrameNav();
+      notifyParentFrameReady();
       try {
         window.parent.postMessage({ type: "instance-theme-ready" }, "*");
       } catch (_) {}
@@ -447,6 +438,7 @@
       syncInlineStyles(get());
       patchHubNavLinks(get());
       observeDynamicLists();
+      if (isHubLinked()) notifyParentFrameReady();
     };
     if (document.readyState === "loading") {
       document.addEventListener("DOMContentLoaded", onReady);