fix: remove vertical margin from checklist nested in a list

A checklist nested inside any list (bullet, ordered, or another checklist)
no longer carries the 1em vertical margin of a top-level checklist. Since
both list_item and checkbox_item render as li elements, target any
checklist-wrapper inside an li rather than only those inside another wrapper.

https://claude.ai/code/session_01BGH191WyuL9SgQyjfJ3YsD

shared/editor/components/Styles.ts

@@ -1478,11 +1478,11 @@ ol li {
 .${EditorStyleHelper.checklistWrapper} {
   position: relative;
   margin: 1em 0;
+}
 
-  .${EditorStyleHelper.checklistWrapper} {
-    position: static;
-    margin: 0;
-  }
+li .${EditorStyleHelper.checklistWrapper} {
+  position: static;
+  margin: 0;
 }
 
 .${EditorStyleHelper.checklistCompletedToggle} {