fix splitting layout bug - was not splitting visually original shell

internals/auth.go

@@ -92,3 +92,24 @@ func isAuthed(r *http.Request) bool {
 	c, err := r.Cookie(authCookieName)
 	return err == nil && validAuthToken(c.Value)
 }
+
+// refreshAuthCookie issues a fresh auth cookie, extending the session TTL
+// (sliding window). No-op in -nopw mode or if current token is already invalid.
+func refreshAuthCookie(w http.ResponseWriter, r *http.Request) {
+	if nopwMode {
+		return
+	}
+	c, err := r.Cookie(authCookieName)
+	if err != nil || !validAuthToken(c.Value) {
+		return
+	}
+	http.SetCookie(w, &http.Cookie{
+		Name:     authCookieName,
+		Value:    makeAuthToken(),
+		Path:     "/",
+		HttpOnly: true,
+		Secure:   true,
+		SameSite: http.SameSiteLaxMode,
+		MaxAge:   int(authTokenTTL.Seconds()),
+	})
+}