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/ItemDatabaseAuthoring.cs

@@ -41,7 +41,6 @@ namespace ProjectM.Authoring
                         Tier = def.Tier,
                         StackMax = def.StackMax,
                         EquipSlot = def.EquipSlot,
-                        GrantedAbilityId = def.GrantedAbilityId,
                         Mod0 = ModAt(def, 0),
                         Mod1 = ModAt(def, 1),
                         Mod2 = ModAt(def, 2),