distinct-by-key-reset-cancel-per-item

Per-item pipelines that key on the item id with distinctUntilChangedBy, cancel the previous item's in-flight work before starting the next, and reset the visible state before filling it — so nothing from the previous item can appear under the new one. Use when a detail screen briefly shows the last item's artwork or text, when a slow response overwrites a newer one, or when a field stays populated after moving to an…