pub fn write_start_page(path: &Path, url: &str) -> Result<(), String>Expand description
Write the start page, replacing whatever was there before. Same
temp-file-then-rename crash safety as bookmarks_store::write_bookmarks.
Two windows writing at the same instant still race at the whole-file
level — last write wins — the same accepted limitation every other
single-JSON-file store in this app has.