feat(vigilante): add arena boss succession

design/user-stories/us-016-manage-vigilante-control-panel.md

@@ -29,7 +29,7 @@ As the **Vigilante**, I want a control panel for managing Followers so that I ca
 - [x] The Follower-management screen identifies current Followers and requires confirmation before dismissal.
 - [x] Successful invitations and dismissals refresh the control panel from authoritative current state and notify affected players.
 - [x] The role-control screen allows the Vigilante to relinquish the role only after explicit confirmation.
-- [x] Relinquishing through the control panel uses normal Vigilante replacement and Follower-cleanup rules.
+- [x] Relinquishing through the control panel clears Followers, opens the Vigilante arena challenge, and communicates that outcome accurately.
 - [x] Every action revalidates the running lifecycle and active Vigilante before changing state.
 - [x] Stale or repeated control-panel interactions cannot invite an ineligible player, duplicate an invitation, or dismiss the wrong Follower.
 - [x] Existing `/vigilante invite`, `/vigilante accept`, `/vigilante dismiss`, `/vigilante leave`, and `/tyrant relinquish confirm` commands remain available.
@@ -46,3 +46,4 @@ Automated tests verify default and explicit command entry points, active-Vigilan
 - [Manage a reign through the Tyrant control panel](us-015-manage-tyrant-control-panel.md)
 - [Role and class model](../concepts/role-and-class-model.md)
 - [Use bound role control items](us-017-use-bound-role-control-items.md)
+- [Claim the Vigilante role in the arena](us-019-claim-vigilante-in-arena.md)