fix(combat): escape occupied login positions

Port retail's radius-aware placement ring so a relogging player is seated beside creatures occupying the saved location, and register the local body in the shared resolved-shadow pipeline. Route new forward movement and jump through AbortAutomaticAttack so repeat combat cancels immediately on movement.

Co-Authored-By: Codex <codex@openai.com>

src/AcDream.Core/Physics/PhysicsEngine.cs

@@ -1325,4 +1325,47 @@ public sealed class PhysicsEngine
 
         return resolveResult;
     }
+
+    /// <summary>
+    /// Runs retail's radius-aware placement-ring search after the host has
+    /// validated the server's cell and grounded the initial position. This is
+    /// the <c>CTransition::find_placement_pos</c> half of enter-world
+    /// <c>SetPosition</c>; unlike an ordinary zero-distance transition it tests
+    /// object occupancy and can seat a relogging player beside a creature that
+    /// now occupies the saved location.
+    /// </summary>
+    public ResolveResult ResolvePlacement(
+        Vector3 position,
+        uint cellId,
+        float sphereRadius,
+        float sphereHeight,
+        float stepUpHeight,
+        float stepDownHeight,
+        ObjectInfoState moverFlags = ObjectInfoState.None,
+        uint movingEntityId = 0)
+    {
+        var transition = new Transition();
+        transition.ObjectInfo.StepUpHeight = stepUpHeight;
+        transition.ObjectInfo.StepDownHeight = stepDownHeight;
+        transition.ObjectInfo.StepDown = true;
+        transition.ObjectInfo.SelfEntityId = movingEntityId;
+        transition.ObjectInfo.State = moverFlags;
+        transition.SpherePath.InitPath(
+            position, position, cellId, sphereRadius, sphereHeight);
+        transition.SpherePath.InsertType = InsertType.Placement;
+
+        bool ok = transition.FindPlacementPos(this);
+        var sp = transition.SpherePath;
+        var ci = transition.CollisionInfo;
+        bool onGround = ci.ContactPlaneValid
+            || transition.ObjectInfo.State.HasFlag(ObjectInfoState.OnWalkable);
+
+        return new ResolveResult(
+            sp.CurPos,
+            sp.CurCellId != 0 ? sp.CurCellId : cellId,
+            onGround,
+            ci.CollisionNormalValid,
+            ci.CollisionNormal,
+            ok);
+    }
 }