Consumable host: initialise at activation, dispose at expiry, instantiate consumables

ActivateConsumable runs Initialize on the effect's behaviours; expiry disposes
them before Resolver.Forget, so a consumable's modifiers exist exactly while
its effect is active. ItemManager.CreateInstance returns a ConsumableItem for a
consumable design. StatResolver.DetachModifier drops an entry left with
nothing attached, so ModifierEntryCount returns to baseline. LoadoutTests'
hand-built ConsumableItem goes through CreateInstance. Builds.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Assets/Scripts/ServerShared/StatResolver.cs

@@ -141,6 +141,9 @@ public class StatResolver
         {
             set.Scale.Remove(modifierKey);
             set.Constant.Remove(modifierKey);
+            // An entry with nothing attached is no entry: a modifier that is gone leaves no trace in the resolver.
+            if (set.Scale.Count == 0 && set.Constant.Count == 0)
+                _modifiers.Remove(entry);
         }
         _cache.Remove(entry);
     }