After a master-user impersonation handoff (GET /api/auth/impersonate) the server
swaps the slot-0 session cookie but the client's persisted account registry
(account-registry / auth-storage in localStorage) still lists the previous
account, so the top-left account chip keeps showing the old mailbox until a
manual sign-out. Redirect impersonation to /?impersonated=1 and add a headless
ImpersonationReconciler that drops the stale persisted account/auth state (and
server-derived caches) then reloads to a clean URL, so the app rehydrates empty
and re-derives the single account from the fresh session. Cookies untouched, so
the just-granted session survives. Runs exactly once.
Reported downstream: shukiv/jabali-panel#646.
