Move scrollbar suppression into the load pipeline and only suppress until load is completed

src/pyj/read_book/iframe.pyj

@@ -260,6 +260,10 @@ class IframeBoss:
         self.content_loaded_stage2()
 
     def content_loaded_stage2(self):
+        # this is the loading styles used to suppress scrollbars during load
+        # added in unserialize_html
+        document.head.firstChild.textContent = ''
+
         self.connect_links()
         self.content_ready = True
         csi = current_spine_item()

src/pyj/read_book/resources.pyj

@@ -239,6 +239,7 @@ def unserialize_html(serialized_data, proceed, postprocess_dom):
     head, body = tree[1], tree[2]  # noqa: unused-local
     clear(document.head, document.body)
     remove_all_attributes(document.head, document.body)
+    document.head.appendChild(E.style(type='text/css', 'html::-webkit-scrollbar, body::-webkit-scrollbar { display: none !important }'))
     # Default stylesheet
     if not runtime.is_standalone_viewer:
         # for the standalone viewer the default font family is set

src/pyj/read_book/settings.pyj

@@ -45,7 +45,7 @@ def apply_colors():
     else:
         text = ''
 
-    ss.textContent = text + '\n\nhtml::-webkit-scrollbar, body::-webkit-scrollbar { display: none !important }'
+    ss.textContent = text
 
 
 def apply_stylesheet():