prependPostCard() now inserts posts in the correct sorted position within
the existing DOM instead of falling back to a full renderFeed() rebuild
when a post is older than the first visible post. This handles relays
that deliver events out of order without wiping the feed.
Also fixed a race condition in fetchFeedWindow: the fire-and-forget
ndkFetchEvents callback was calling renderFeed() after bootstrap
completed, which wiped prepended live posts and caused concurrent
rebuild races. Now it only calls renderFeed() if the feed hasn't been
rendered yet (renderedPostIds.size === 0).
Same prependPostCard sorted-insert fix applied to post.html.
Laan Tungir
04405da933