Add IEncounterCompleteEventStore with in-memory implementation, record
events on successful TryCompleteAndGrant, and expand reward_delivery
hook comments for future QuestRewardBundle routing.
In-memory IEncounterProgressStore and IEncounterCompletionStore with
EncounterProgressOperations for activation, defeat tracking, and
all-targets-defeated checks; unit tests and docs.
Thin IEncounterDefinitionRegistry / IRewardTableDefinitionRegistry adapters
over NEO-101 catalogs with TryNormalizeKnown, DI registration, and 18 AAA tests.