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/Simulation/Player/MeleeComboSystem.cs

@@ -248,13 +248,9 @@ namespace ProjectM.Simulation
                             SourceNetworkId = c.OwnerId,
                             SourceTick = c.Stamp,
                         });
-                        if (c.KnockSpeed > 0f && m_KnockbackLookup.HasComponent(target) && !m_BossLookup.HasComponent(target))
-                        {
-                            float3 d3 = enemyPositions[i] - c.From;
-                            float2 kdir = new float2(d3.x, d3.z);
-                            kdir = math.lengthsq(kdir) > 1e-6f ? math.normalize(kdir) : c.Face;
-                            m_KnockbackLookup[target] = new KnockbackState { Dir = kdir, Speed = c.KnockSpeed, UntilTick = c.KnockUntil };
-                        }
+                        if (c.KnockSpeed > 0f)
+                            KnockbackUtil.Stamp(ref m_KnockbackLookup, m_BossLookup, target,
+                                c.From, enemyPositions[i], c.Face, c.KnockSpeed, c.KnockUntil);
                     }
                 }
                 // HARVEST: deplete every node/clutter in each swing's cone, crediting the shared ledger; write