feat(vigilante): add arena boss succession

design/user-stories/us-010-handle-inactivity-and-selection.md

@@ -15,14 +15,15 @@ As a **participant**, I want inactive central roles to be replaced fairly so tha
 - [x] Random candidates are drawn from eligible opted-in players who logged in during the preceding 24 hours.
 - [x] The Tyrant is always excluded from Vigilante selection.
 - [x] A previous role holder is excluded when another eligible candidate exists and may be reused only as a fallback.
-- [x] Tyrant inactivity ends the reign, clears all assignments, and invokes normal random Tyrant succession followed by Vigilante selection.
-- [x] Vigilante inactivity clears Followers and rerolls only the Vigilante position.
+- [x] Tyrant inactivity ends the reign, clears all assignments, invokes normal random Tyrant succession, and opens the Vigilante arena challenge once a Tyrant is active.
+- [x] Vigilante inactivity clears Followers and opens the Vigilante arena challenge without changing the Tyrant.
 - [x] An offline randomly selected candidate must log in within 24 unpaused hours to confirm the assignment.
-- [x] An unconfirmed selection expires and rerolls automatically under the same eligibility rules.
-- [x] Selection remains vacant and retries periodically when no valid candidate exists.
+- [x] An unconfirmed Tyrant selection expires and rerolls automatically under the same eligibility rules.
+- [x] Tyrant selection remains vacant and retries periodically when no valid candidate exists.
 - [x] Candidate selection cannot assign conflicting roles or choose an opted-out player, including during concurrent joins and deaths.
 
 ## Related
 
 - [Tyrant game state machine](../concepts/game-state-machine.md)
 - [Inform players and manage participation](us-011-inform-and-manage-participation.md)
+- [Claim the Vigilante role in the arena](us-019-claim-vigilante-in-arena.md)