Protection from spells checks can fail

_Devoted Caretaker_ can give protection from instant + sorcery **spells**[^1]

Case A:
➡️ the cast trigger of _The Beast, Deathless Prince_ will be from a spell source, so it shouldn't be able to target it now

Case B:
➡️ but the trigger from _Kozilek's Return_ should be allowed to damage it, since the ability triggers in the GY

Ideas:
1. I think ideally `Card.isSpell()` could be changed from
- `isInstant() || isSorcery() || (isAura() && !isInZone(ZoneType.Battlefield))`
to just
- `isInZone(ZoneType.Stack)`
But I'm not sure if some that would fail some logic checks?

2. Maybe just scripting it as `Protection:Instant.inZoneStack,Sorcery.inZoneStack` is the safer alternative

3. Otherwise `getProtectionValid` will need a bigger rework as it also needs to provide SA valids:
- but not for all parts
- Damage replacement would somehow need to check the Cause instead (but only if DamageSource is its host?) 🤔

[^1]: So it's different from e. g. _Petrified Wood-Kin_ which has "Protection from instants", here only the type should matter