bug: Actionbar written by two systems simultaneously — causes flicker

[TheMeinerLP]

Description

Both `ScoreDisplaySystem` (ECS) and `GameHud` write to the player actionbar independently. Because they run on different schedules, the client receives two competing actionbar packets per tick, causing visible flicker and inconsistent display.

Acceptance Criteria

• Exactly one system is responsible for writing the actionbar per player
• `ScoreDisplaySystem` is either removed or repurposed to feed data to `GameHud` rather than writing directly
• `GameHud` is the single actionbar writer, combining score + HUD info in one formatted string
• No flicker observable at 20 TPS

Technical Details

• Consolidation point: `GameHud.tick()` or a new `HudAggregatorSystem`
• `ScoreDisplaySystem` should push its data into a `HudDataComponent` that `GameHud` reads
• Alternatively: delete `ScoreDisplaySystem` and move its logic directly into `GameHud`

Dependencies

• Live scoreboard issue (actionbar role may change once sidebar carries ranking data)

Estimate

S