LANTERN purge B6: delete the legacy single-ability path (sockets are THE ability model)

AbilityRef, AbilityCooldown, EffectiveAbilityStats, DefaultAbility deleted.
GoInGameServerSystem seeds the per-frame 4-socket Spark loadout UNCONDITIONALLY
(was gym-only); ClassSelectReceiveSystem + DebugOp.SetClass swap FrameId +
re-seed sockets + zero SocketCooldown; ClassSwapUtil.Apply drops newAbilityId;
EquipSystem weapons become stat-sticks (GrantedAbilityId removed from the item
blob/authoring); StatRecomputeSystem folds CharacterStatsRef + sockets only;
HUD cooldown bar reads socket 0 of SocketCooldown/EffectiveSocketStats; class
HUD readers are FrameId-only (ClassForAbility/AbilityFor deleted);
DebugModifierInjectionSystem drops CycleAbility.

390 tests green; Play-verified: a non-gym spawn gets frame=2 with Sparks
[7,8,6,9] and no console errors.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Assets/_Project/Scripts/Authoring/Items/ItemDefinition.cs

@@ -33,9 +33,6 @@ namespace ProjectM.Authoring
         [Tooltip("EquipSlotId byte: 0=Weapon, 1=Armor, 2=Trinket, 3=Tool, 255=not equippable.")]
         public byte EquipSlot = 255;
 
-        [Tooltip("AbilityId granted when equipped in the Weapon slot (0=none): 1=Primary, 2=FastLight, 3=SlowHeavy.")]
-        public byte GrantedAbilityId = 0;
-
         [Tooltip("Stat modifiers granted while equipped (first 4 used).")]
         public List<ItemModAuthoring> Mods = new List<ItemModAuthoring>();
     }