feat(battle-engine-port): M2 step 1 — SingleBattleMgr constructs headless

First green of the M2 go/no-go probe: `new SingleBattleMgr(StandardBattleMgr-
ContentsCreator)` now builds the two-player pair fully headless against the shim,
no Unity runtime. Verdict: headless construction is feasible; every blocker was a
mechanical no-op shim fill or data seam, not a Unity/logic wall.

Shim fills (authored):
- GameMgr: lazy non-null DataMgr/PrefabMgr/InputMgr/SoundMgr/BattleControl.
- GameObject: lazy cached component model so GetComponent<T>/AddComponent<T> return
  non-null no-op instances for Component-derived T (F1: unguarded view touches).
- Resources.Load(string): cached non-null GameObject so the prefab->Instantiate->
  GetComponent chain (UnityEventAgent) yields a real object.
- ClassBattleCardViewBase: re-attach dropped IClassBattleCardView (no-op members);
  ClassBattleCardBase.Setup casts the created view to it.

Engine copy (DP1/DP3 mis-cut fix):
- CardIconControl.cs copied verbatim (manifested) + generated null-stub deleted.
  SplitAndCompleteIconStr is pure string logic on the resolution path that M1 had
  wrongly stubbed as "View" -> null deref in SkillCreator.CreateBuildInfo.

Test harness (SVSim.BattleEngine.Tests, authored fixture):
- HeadlessContentsCreator/HeadlessPhaseCreator: deterministic replica of the solo
  practice init (StandardBattleMgrContentsCreator + SingleBattlePhaseCreator) with
  no-op recovery/replay managers.
- HeadlessCardMaster: reflects the loader cards.json dump into CardMaster.
- HeadlessMasterData: minimal Data.Master (class-character list, empty collections)
  + Data.Load + player/enemy chara ids.
- ConstructionProbeTests.SingleBattleMgr_constructs_headless — GREEN.

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

SVSim.BattleEngine/Shim/View/SettingsUiStubs.cs

@@ -48,7 +48,18 @@ namespace Wizard.Battle.View
 {
     // Decomp bases (dropped by the hand stub): both derive from BattleCardView, which
     // carries the IBattleCardView impl — so they convert to IBattleCardView via it.
-    public abstract class ClassBattleCardViewBase : BattleCardView { }
+    // The decomp ClassBattleCardViewBase also implements IClassBattleCardView; the resolution
+    // path casts the created view to it (ClassBattleCardBase.Setup), so re-attach the dropped
+    // interface here with no-op members (the leaf PlayerClassBattleCardView inherits them).
+    public abstract class ClassBattleCardViewBase : BattleCardView, IClassBattleCardView
+    {
+        public virtual Wizard.Battle.Player.ClassCharacter.IClassCharacter ClassCharacter => null;
+        public virtual void StartOutFrame() { }
+        public virtual void StartIntoFrame() { }
+        public virtual float GetCurrentClipTime() => 0f;
+        public virtual bool GetCurrentClipIsName(global::ClassCharaPrm.MotionType motionType) => false;
+        public virtual void ClearSpineObject() { }
+    }
     public class NullBattleCardView : BattleCardView { public NullBattleCardView() { } public NullBattleCardView(BuildInfo buildInfo) { } public static void ReleaseSharedDummy() { } }
 }