fix(model): ModelScene spell animations do not play over a death

A unit without health plays only death animations: CGUnit_C::
PlayAnimation (0x005FE2F0) returns unless IsDeathAnimation (0x005FDA90,
__stdcall) holds for the animation. An actor had no such gate, so a
missile already in flight when the target died still played its wound
(and its impact kit's animation) on arrival and replaced the death
animation; StopSpellVisual only drops the casts still preparing.

An actor whose own animation is a death animation now takes no kit
animation over it, and setting a death drops the kit animation that
plays. The missiles still land and show their impact effects.

Author: brues-code

src/Offsets.h

@@ -6376,6 +6376,10 @@ enum Offsets {
     // right hand (attachment 1) for the main-hand lane and the left (2) for
     // the off hand (AttachItemModel 0x0047A0C0).
     FUN_M2MODEL_HAS_ANIMATION = 0x00711960,
+    // IsDeathAnimation `int __stdcall(int anim)`, ret 4 (a jump table). A
+    // dead unit plays only death animations: CGUnit_C::PlayAnimation
+    // (0x005FE2F0) returns for health below 1 unless the animation is one.
+    FUN_IS_DEATH_ANIMATION = 0x005FDA90,
     ANIM_STAND = 0,
     ANIM_BOW_PULL = 160,
     ANIM_BOW_RELEASE = 161,

src/model/SceneActor.cpp

@@ -461,9 +461,26 @@ void Actor::ClearModel() {
     RunScript(S_ONMODELCLEARED, 0);
 }
 
+namespace {
+
+bool IsDeathAnimation(int anim) {
+    return reinterpret_cast<int(__stdcall *)(int)>(Offsets::FUN_IS_DEATH_ANIMATION)(anim) != 0;
+}
+
+} // namespace
+
+// An actor whose own animation is a death animation is dead to its spells, as
+// a unit without health is to its PlayAnimation (0x005FE2F0): a kit's
+// animation (a cast, an impact, a wound) does not play over the death, and a
+// death drops the one that plays.
 void Actor::PlayAnimation() {
     if (model == nullptr)
         return;
+    if (kitAnimation >= 0 && IsDeathAnimation(static_cast<int>(animation)) && !IsDeathAnimation(kitAnimation)) {
+        kitAnimation = -1;
+        kitAnimationLoops = false;
+        kitAnimationEnded = true;
+    }
     heldPositionMs = -1; // a paused actor holds the new animation's first frame
     // An end the scene's advance reported for the animation this replaces is
     // not this one's: the engine reports a replaced play as reason 1, which