Policy-limits fetch now uses an AbortController and reports cycle_aborted

The component that fetches policy limits now uses an AbortController to cancel in-flight network requests. Its abort signal is passed into the fetch call and gets recreated whenever the fetcher is stopped. If a fetch is aborted, or if the session generation changes mid-flight, the outcome is now logged as cycle_aborted, and the fetchAndLoad function checks for this aborted state in addition to its previous check for a changed session generation.