feat(progress): track persistent creeper kills

design/user-stories/us-003-show-progression-and-rank-advancement.md

@@ -1,7 +1,7 @@
 ---
 type: User Story
 title: "US-003: Show progression and rank advancement"
-description: Give players brief kill progress displays and prominent rank-up notifications.
+description: Give players brief current-tier progress displays and prominent rank-up notifications.
 status: backlog
 ---
 
@@ -12,15 +12,14 @@ As a **player**, I want visible progress and rank-up notifications so that I und
 ## Acceptance criteria
 
 - [ ] After each qualifying creeper kill, a temporary boss bar shows the player's current state and progress toward the next rank.
-- [ ] A locked player sees progress toward Creeper Aura I.
-- [ ] A ranked player sees their current Roman-numeral rank, current kill total, and the next threshold.
+- [ ] A locked player sees current-tier progress toward Creeper Aura I.
+- [ ] A ranked player sees their current Roman-numeral rank, current-tier progress, and the next rank requirement.
 - [ ] The display duration is configurable and defaults to a short period measured in seconds.
 - [ ] The boss bar is hidden automatically when its display period expires.
 - [ ] A rank VI player no longer sees a progress boss bar.
 - [ ] Each newly attained rank displays a full-screen title naming the rank.
 - [ ] Joining the server does not replay a previously acknowledged rank-up title.
-- [ ] Administrative progress changes update the display state of an online affected player.
-- [ ] When one progress event satisfies multiple ranks, the resulting rank and notification behavior is deterministic and tested.
+- [ ] Administrative changes update an online player's boss bar if it is currently visible.
 
 ## Related