A `persist:` partition's cookie store hydrates lazily, so the first
cookies.get() on a fresh launch can return empty for a signed-in user.
That false-negative made hasLiveOauthSession() throw "not signed in",
which on the no-retry initial boot path surfaced as the transient
"Hermes couldn't start" OAuth overlay that always cleared on Retry.
hasLiveOauthSession now reads once (no added latency on the happy path);
only on an empty read does it warm the store (flushStorageData + a
throwaway get, memoized) and re-read with a bounded ~180ms backoff
before trusting the negative. Genuinely signed-out users still resolve
false quickly and get the overlay. Fixes the whole class: the same
function backs the reconnect path and the Settings connected indicator.