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/Simulation/Items/DefaultAbility.cs

@@ -1,17 +0,0 @@
-using Unity.Entities;
-
-namespace ProjectM.Simulation
-{
-    /// <summary>
-    /// The player's "unarmed" / base ability id, baked from PlayerAuthoring.PrimaryAbility. Restored into
-    /// <see cref="AbilityRef"/>.Id by EquipSystem when a weapon is unequipped. NOT replicated (it never changes,
-    /// so a [GhostField] would waste snapshot bytes and there is no client consumer). AbilityRef itself cannot
-    /// serve double duty because EquipSystem overwrites AbilityRef.Id when a weapon is equipped — this preserves
-    /// the immutable default to fall back to. Server-read only.
-    /// </summary>
-    public struct DefaultAbility : IComponentData
-    {
-        /// <summary>The <see cref="AbilityId"/> (as a byte) the player fires with no weapon equipped.</summary>
-        public byte Id;
-    }
-}

Assets/_Project/Scripts/Simulation/Items/DefaultAbility.cs.meta

@@ -1,2 +0,0 @@
-fileFormatVersion: 2
-guid: 4c6831e7f8bb98d448917f88dcbe12db

Assets/_Project/Scripts/Simulation/Items/ItemDatabaseBlob.cs

@@ -50,9 +50,6 @@ namespace ProjectM.Simulation
         /// <summary>Equip slot (see <see cref="EquipSlotId"/>); 255 = not equippable.</summary>
         public byte EquipSlot;
 
-        /// <summary>AbilityId granted when equipped in the Weapon slot (0 = none); the equip handler writes it into AbilityRef.Id.</summary>
-        public byte GrantedAbilityId;
-
         /// <summary>Up to <see cref="MaxMods"/> INLINE stat-mod grants applied while equipped (Target 255 = unused). Inline, not a nested BlobArray.</summary>
         public ItemModSpec Mod0, Mod1, Mod2, Mod3;