When the AppView indexes a new post quickly, briefly flashing the
spinner before it morphs into the success toast feels glitchy. Add a
`loadingDelay` option to Toast.promise() so the loading toast is only
rendered if the promise hasn't settled within the delay; otherwise we
jump straight to success/error.
Default is 0 (immediate, matching the existing behaviour). The composer
opts in to a 500ms delay so the common fast path shows only the success
toast.
Claude
31aa4a4f40