## Problem
`GetMonsterAbilities()` answers three questions through one virtual: which abilities a creature has (`GetAbility`, `AOS.cs` reflect/barrier, bard fire-breath difficulty), which abilities are enabled right now, and where cooldown state must be cleaned up (`InvalidateNextAbilityTriggers` on death and delete). Every caller assumes it is a pure, stable list. About 70 creatures return a static array; only LordOaks computed it:
```
Mobile.Delete()
→ BaseCreature.OnDelete() → CreatureDeletedEvent
→ MonsterAbility.InvalidateNextAbilityTriggers()
→ LordOaks.GetMonsterAbilities() → CheckQueen() → new Silvani().MoveToWorld(...)
```
- Deleting a Lord Oaks nobody had fought (champion reset, `DeleteCreatures`, GM delete) spawned an orphaned Silvani where he stood.
- The spell damage scalar (`AlterDamageScalarFrom`) spawned her too.
- With the queen dead his list was empty, so cleanup skipped his cooldown entries. The static `Dictionary<BaseCreature, long>` on the ability singleton kept a reference to the deleted creature. `MonsterAbilityGroup` children's entries were never cleaned either.
- Neira threw unholy bones from `AlterDamageScalarFrom`, so any caller asking for a damage scalar (a preview gump, for example) could fire the effect.
## Changes
- **Per-creature cooldowns:** a lazy `Dictionary<MonsterAbility, long>` on `BaseCreature` (`IsAbilityOnCooldown`, `SetAbilityCooldown`, `ClearAbilityCooldowns`). The static dictionaries and the query-driven cleanup are gone, and death still resets cooldowns. Tick comparisons are wraparound-safe.
- **Pure contract:** `GetMonsterAbilities()` is documented as pure. The new `virtual bool CanUseAbility(MonsterAbility)` gates abilities that only work some of the time. Every `TriggerAbility*` loop and `GetAbility` check it.
- **LordOaks:** always lists his abilities; `CanUseAbility` and the 10% spell shield read "queen alive". The queen spawns when he is first aggressed or first given a combatant, never on the internal map. Aggression lands before the damage it causes, so the first spell is still shielded, as before.
- **Neira:** the unholy bone throw moves to `OnDamagedBySpell`.
A follow-up PR makes minions such as the queen, pixies and Barracoon's rats belong to their champion spawn, so a spawn reset cleans them up.
## Testing
- `LordOaksTests` covers three cases:
- querying or deleting an unengaged Lord Oaks spawns nothing;
- aggression spawns the queen exactly once, and the shield and abilities follow her life;
- an Oaks on the internal map never spawns her.
- UOContent.Tests: 1234 passed, 2 skipped.
- A local constructor sweep (every Mobile built and deleted repeatedly) no longer reports LordOaks.
