feat(battle-engine-port): M3 COMPLETE — fixed-damage spell resolves headless (leader-life-delta oracle passes)

Card 900124030 (ELF cost-3, when_play damage=3 to enemy leader) resolves to
correct authoritative state headless via the IsForecast/IsRecovery +
ActionProcessor.PlayCard path. New oracle dimension (opponent leader-life delta)
passes; 3/3 tests green; engine still 0 errors; check_drift clean.

Four headless gaps, each mechanical (no logic/Unity wall):
- Data seam: InitLeaderLife (SetupInitialGameState->InitializeClassLife subset);
  leader BaseMaxLife was 0 => game-over => play silently rejected. M2 missed it
  (only asserted leader life unchanged: 0==0).
- Runtime cast: re-attach IClassBattleCardView on the generated
  NullClassBattleCardView stub (members already present; base-clause recovery
  stripped the decl). Compiled fine -> M1 loop never surfaced it.
- M1 mis-cut: copy NullVfxWithLoading verbatim (its GetInstance() lazy singleton
  was stubbed to default!/null). Same pattern as M2 NullCardVfxCreator.
- Card events: CreateHeadlessHandCard now calls SetupCardEvent so a spell's
  OnPlay->RemoveSpellCardFromHand / OnFinishWhenPlaySkill->AddSpellCardToCemetery
  fire (the bare CreateCardWithoutResources seam skips them).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

SVSim.BattleEngine/Shim/View/SettingsUiStubs.cs

@@ -61,6 +61,16 @@ namespace Wizard.Battle.View
         public virtual void ClearSpineObject() { }
     }
     public class NullBattleCardView : BattleCardView { public NullBattleCardView() { } public NullBattleCardView(BuildInfo buildInfo) { } public static void ReleaseSharedDummy() { } }
+
+    // The decomp NullClassBattleCardView is `: NullBattleCardView, IClassBattleCardView, IBattleCardView`;
+    // base-clause recovery kept only the base class. IBattleCardView is satisfied via the BattleCardView
+    // base, but IClassBattleCardView was dropped. The generated NullClassBattleCardView stub already
+    // provides that interface's members (public no-ops), so just re-attach the dropped interface here.
+    // The resolution path's VirtualClone (createNullView) -> ClassBattleCardBase.Setup casts the null
+    // view to IClassBattleCardView, which throws InvalidCastException at runtime without this (M3,
+    // fixed-damage spell: Skill_damage.TakeDamageSingle clones the leader before applying damage).
+    // Compiles fine without it (it's a cast, not a member call), so the M1 loop never surfaced it.
+    public partial class NullClassBattleCardView : IClassBattleCardView { }
 }
 
 namespace Wizard.Battle.View.Vfx