After each state-mutating dispatch, evaluate world.endings in priority
order (true > wrong > bad). The first whose whenFlags are all satisfied
sets state.endedWith and appends a kind:'ending' transcript line. Once
ended, further dispatches return a "story has ended" narration.
Also update test-world fixtures and placeholder ending markdown files
to use whenFlags: { _never: true } instead of {} so that vacuously-true
empty flags don't accidentally fire on every successful turn.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
ejlewis