Hygiene B4c: clean dedup helpers (knockback, bakers, editor rig)

- KnockbackUtil.Stamp: shared knockback-stamp used by AbilityFireSystem + MeleeComboSystem (guard + planar normalize + write; speed passed in).
- BakerStructureExt: AddPlacedStructure/AddDamageable extensions on Baker<T>; rewired Turret/Structure/Harvester/Conveyor/Fabricator bakers (baked data + serialized fields unchanged).
- EnemyPrefabBakeExt.AddEnemyPrefabPool: shared prefab-buffer bake for ZoneEnemyDirector/WaveDirector authoring (fields stay flat — no serialization change).
- Editor AnimRigUtil (HasParam + root-yaw overlay clip) shared by PlayerRigTools/EnemyRigTools; EnemyRigTools.MakeMat now GUID-preserving (CopySerialized over existing) — the composite AnimatorController copy left as-is with a caveat comment.

466/466 EditMode tests pass, 0 warnings.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Assets/_Project/Scripts/Editor/PlayerRigTools.cs

@@ -30,22 +30,11 @@ namespace ProjectM.EditorTools
             // Full idle pose (every bone keyed) + a Root yaw twist. See the class summary for why a Root-only clip sinks.
             var clip = AssetDatabase.LoadAssetAtPath<AnimationClip>(SwingClip);
             if (clip == null) { clip = new AnimationClip { frameRate = 30f }; AssetDatabase.CreateAsset(clip, SwingClip); }
-            clip.ClearCurves();
-            foreach (var b in AnimationUtility.GetCurveBindings(idle))
-            {
-                if (b.path == "Root") continue; // the Root is driven below
-                AnimationUtility.SetEditorCurve(clip, b, AnimationUtility.GetEditorCurve(idle, b));
-            }
             var yaw = new AnimationCurve(
                 new Keyframe(0f, 0f), new Keyframe(0.06f, -25f), new Keyframe(0.16f, 48f), new Keyframe(0.30f, 0f));
-            AnimationUtility.SetEditorCurve(clip, EditorCurveBinding.FloatCurve("Root", typeof(Transform), "localEulerAnglesRaw.y"), yaw);
-            var s = AnimationUtility.GetAnimationClipSettings(clip);
-            s.loopTime = false;
-            AnimationUtility.SetAnimationClipSettings(clip, s);
-            EditorUtility.SetDirty(clip);
-            AssetDatabase.SaveAssets();
+            AnimRigUtil.BuildRootYawOverlayClip(clip, idle, yaw);
 
-            if (!HasParam(ac, "IsAttacking"))
+            if (!AnimRigUtil.HasParam(ac, "IsAttacking"))
                 ac.AddParameter("IsAttacking", AnimatorControllerParameterType.Bool);
 
             var sm = ac.layers[0].stateMachine;
@@ -80,12 +69,6 @@ namespace ProjectM.EditorTools
             return null;
         }
 
-        static bool HasParam(AnimatorController ac, string name)
-        {
-            foreach (var p in ac.parameters) if (p.name == name) return true;
-            return false;
-        }
-
         static AnimatorState FindState(AnimatorStateMachine sm, string name)
         {
             foreach (var c in sm.states) if (c.state.name == name) return c.state;