The subset of LaunchDarkly's LDFlagsState this provider reads.
getFlagValue is the synchronous read that makes a LaunchDarkly-backed
implementation of the synchronous IFeatureFlags.isEnabled possible at all:
the state object is fetched asynchronously once, then queried synchronously.
readonly
valid: boolean
False when the snapshot could not be computed (client offline, no context).
getFlagValue(key: string): unknown
Reads one flag's value from the recorded snapshot.