changed my mind on maintainVisibleContentPosition

Remove the dead contentOffset prop from List and add
maintainVisibleContentPosition to anchor the visible item across
relayouts.

The negative contentOffset was originally paired with a matching
contentInset (web PR #230) so the first render sat flush under the
floating header. PR #2216 swapped the inset for a paddingTop style but
left the offset behind, where it's been dead on initial render since.
On rotation its value changes (it's partly derived from the top safe
-area inset), and RN re-applies it as an absolute scroll, snapping the
list. maintainVisibleContentPosition then keeps the visible post pinned
as items reflow to the new width.

APP-2315

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/view/com/util/List.tsx

@@ -147,12 +147,10 @@ let List = forwardRef<ListMethods, ListProps>(
       )
     }
 
-    let contentOffset
     if (headerOffset != null) {
       style = addStyle(style, {
         paddingTop: headerOffset,
       })
-      contentOffset = {x: 0, y: headerOffset * -1}
     }
 
     return (
@@ -170,7 +168,6 @@ let List = forwardRef<ListMethods, ListProps>(
           ...props.scrollIndicatorInsets,
         }}
         indicatorStyle={t.scheme === 'dark' ? 'white' : 'black'}
-        contentOffset={contentOffset}
         refreshControl={refreshControl}
         onScroll={scrollHandler}
         scrollsToTop={scrollsToTop}