Cached fetches no longer issue a /cache_keys preflight per call. The client
trusts whatever it has in IDB and keeps it fresh through ActionCable
broadcasts and the existing reconnect-time batch revalidate.
On warm boots a new hydrateStoresFromCache helper seeds Vuex from IDB
before ActionCable connects, so inboxes, labels, teams, canned responses,
and agents render immediately from cache. The helper snapshots local cache
keys before fetching server keys — without that ordering the comparison
would always see "fresh" against the just-written key and stale data would
be served forever. Stale entries are revalidated in the background; cold
devices stay on the network-fetch path with no regression.
Also awaits replace inside refetchAndCommit so the data write completes
before the cache key is persisted, closing a window where a concurrent
reader could see a fresh key paired with stale data.
Shivam Mishra