Keep API not-found and 401 responses usable behind Ingress and in the Web UI.

Return native JSON with the missing id in the message, clear stale sessions on
401, and document ingress-nginx annotations so branded HTML 404/405 pages do
not rewrite simulator bodies.

app/web/index.html

@@ -6228,6 +6228,21 @@
       }
     }
 
+    async function clearSession(options = {}) {
+      const { toastMessage = null, toastKind = "info", closePanel = true } = options;
+      state.ticket = null;
+      state.csrf = null;
+      state.username = null;
+      document.cookie = "vmware-api-session-id=; Max-Age=0; path=/; SameSite=Strict";
+      try { localStorage.removeItem(LS_AUTH); } catch { /* ignore */ }
+      try { sessionStorage.removeItem(LS_AUTH); } catch { /* ignore */ }
+      setAuth(false);
+      persistAuth();
+      if (closePanel) closeAuthPanel();
+      resetClusterStats("—");
+      if (toastMessage) toast(toastMessage, toastKind);
+    }
+
     async function logout() {
       try {
         if (state.ticket) {
@@ -6240,15 +6255,15 @@
       } catch (error) {
         console.warn(error);
       }
-      state.ticket = null;
-      state.csrf = null;
-      state.username = null;
-      document.cookie = "vmware-api-session-id=; Max-Age=0; path=/; SameSite=Strict";
-      setAuth(false);
-      persistAuth();
-      closeAuthPanel();
-      resetClusterStats("—");
-      toast("Signed out", "info");
+      clearSession({ toastMessage: "Signed out", toastKind: "info" });
+    }
+
+    function expireSession() {
+      clearSession({
+        toastMessage: "Session expired — sign in again",
+        toastKind: "warn",
+        closePanel: false,
+      });
     }
 
     function updateStatusBadge(status) {
@@ -6340,6 +6355,9 @@
       const text = await res.text();
       let parsed;
       try { parsed = JSON.parse(text); } catch { parsed = text; }
+      if (res.status === 401 && (state.ticket || state.username)) {
+        expireSession();
+      }
       return { status: res.status, body: parsed, durationMs: Math.round(performance.now() - started) };
     }