fix(arena): improve containment and boss idle

design/log.md

@@ -6,6 +6,13 @@ description: Chronological record of material decisions affecting the Spigot Tyr
 
 # Spigot Tyrant Design Log
 
+## 2026-08-23 — Arena containment and idle boss corrected
+
+- Corrected shared-arena containment with a validated 12-block barrier wall extending below the arena floor and active-fight block placement and breaking protection.
+- Kept red or blue role particles visible at multiple wall heights during fights so challengers can see the otherwise invisible barrier from inside.
+- Arena bosses now remain AI-disabled at the center until an eligible challenger enters, move normally within the arena during combat, and return healed and idle only on reset or boundary escape.
+- Verified wall geometry, safe restoration, boundary visibility policy, build protection, idle/combat boss transitions, configuration validation, compiler warnings, 119 automated tests, and packaging with `./gradlew clean check jar`.
+
 ## 2026-08-23 — Shared Tyrant and Vigilante arena succession completed
 
 - Completed US-020 and reopened related succession, inactivity, administration, configuration, and Vigilante-arena stories so non-player Tyrant replacement is earned rather than random.

design/user-stories/us-012-configure-and-persist-state.md

@@ -11,7 +11,7 @@ As a **server operator**, I want configurable and durable game behavior so that
 
 ## Acceptance criteria
 
-- [x] Configuration covers ranges, durations, cooldowns, inactivity and maintenance intervals, effect levels and caps, mob restrictions, item materials and names, messages, timer behavior, and shared-role-arena boss balance.
+- [x] Configuration covers ranges, durations, cooldowns, inactivity and maintenance intervals, effect levels and caps, mob restrictions, item materials and names, messages, timer behavior, shared-role-arena boss balance, and a validated barrier wall height defaulting to 12 blocks.
 - [x] Defaults match the approved user stories, including a 50-block Tyrant range and Follower range, seven-day opt-out, 48-hour inactivity, and one-minute role maintenance.
 - [x] Invalid required configuration prevents partial plugin initialization and produces a clear server log message.
 - [x] UUID-keyed state stores lifecycle, current and pending roles, assignments, login history, participation, reign progression, purchases, choices, cooldowns, paused time, item delivery, and captured mobs; the administrator-set arena center is durable across restarts.

design/user-stories/us-019-claim-vigilante-in-arena.md

@@ -17,11 +17,14 @@ As an **opted-in participant**, I want a visible one-player boss challenge for a
 - [x] The challenge boss defaults to an armored, 80-health enhanced zombie, does not burn in sunlight, and remains within a default 10-block-radius arena.
 - [x] All online opted-in players are told when the role opens and receive the arena world and coordinates; opted-in players receive the same notice when they log in while it remains open, and opted-out players do not.
 - [x] Exactly one eligible opted-in non-Tyrant player may enter as challenger, including when entry is attempted by walking or teleportation.
-- [x] Starting a fight replaces the passive particle boundary with temporary actual `BARRIER` blocks that are removed safely without permanently changing existing blocks.
+- [x] Starting a fight builds temporary actual `BARRIER` blocks from one block below the arena floor through a default 12-block wall height, without permanently changing existing blocks.
+- [x] Role-colored boundary particles remain visible from inside and outside an active fight at multiple wall heights.
 - [x] Any non-challenger who enters or respawns inside the arena is moved safely outside it.
 - [x] Existing mobs in the arena and mobs that spawn or enter it are removed while preserving the arena boss.
+- [x] With no challenger, the boss remains AI-disabled at the arena center; entry enables its AI and target, while reset restores full health, center position, no target, and disabled AI.
 - [x] The boss attacks only the active challenger, and only that challenger can damage the boss.
 - [x] Challenger death, disconnect, or leaving by any mechanism ends the fight and resets the boss to full health at its spawn; death counts as leaving and the same player may retry immediately.
+- [x] Block placement and breaking are denied inside the arena during an active fight so players cannot build over or modify the boundary.
 - [x] Killing the boss assigns the challenger as Vigilante, removes the boss and barriers, and restores the passive particle boundary.
 - [x] Pausing, resetting, restarting, reloading, and repeated or concurrent events cannot duplicate the boss, barriers, challenger, or Vigilante assignment.
 - [x] If the arena is not configured when a challenge should open, the Vigilante remains vacant and administrators receive a clear warning.

design/user-stories/us-020-claim-tyrant-in-arena.md

@@ -15,7 +15,7 @@ As an **opted-in participant**, I want to earn a vacant Tyrant role through the
 - [x] Tyrant death without a player killer, Tyrant inactivity, and Tyrant relinquishment end the reign, clear all role-side assignments, and open the shared arena with no active or pending Tyrant.
 - [x] The shared arena opens only one role challenge at a time: a vacant Tyrant takes priority, and the Vigilante challenge can open only after a Tyrant becomes active.
 - [x] The passive arena boundary uses red particles for an open Tyrant challenge, blue particles for an open Vigilante challenge, and a neutral marker while neither role challenge is open.
-- [x] The Tyrant challenge uses the existing configured arena, boss balance, mob exclusion, one-challenger barrier, containment, reset, notification, and missing-location rules.
+- [x] The Tyrant challenge uses the existing configured arena, boss balance, tall visible one-challenger barrier, block-change protection, idle-center boss behavior, containment, reset, notification, and missing-location rules.
 - [x] An eligible opted-in participant, including the former Tyrant, may challenge for the vacant Tyrant role; an active Tyrant cannot enter any arena fight.
 - [x] Defeating the Tyrant challenge boss assigns the challenger as Tyrant with level zero, no purchases, and exactly one starting unlock choice.
 - [x] Completing the Tyrant challenge immediately permits the blue Vigilante challenge to open at the same location when the Vigilante role is vacant.