On shutdown the full article list (including current read/unread state)
and the ID of the open article are saved to
~/.local/share/net.jeena.FeedTheMonkey/cache.json.
On next launch:
- The cached articles are loaded into the list immediately, before any
network request, so the sidebar is populated and the previously open
article is visible without waiting for the server.
- The article content is injected into the WebView once its base HTML
finishes loading (LoadEvent::Finished), avoiding a race where
window.setArticle() did not yet exist.
- A background refresh then fetches fresh data from the server; if the
previously open article still exists its selection is preserved,
otherwise the first item is selected.
- Network errors during a background refresh show a toast instead of
replacing the visible article list with an error page.
