Move ntree to mjModel allocator sizes

PiperOrigin-RevId: 795855203
Change-Id: Idab185294d53dced9ebf073b782969dc5643b95a

include/mujoco/mjmodel.h

@@ -654,6 +654,7 @@ struct mjModel_ {
   int nbvhdynamic;                // number of dynamic bounding volumes (aabb stored in mjData)
   int noct;                       // number of total octree cells in all meshes
   int njnt;                       // number of joints
+  int ntree;                      // number of kinematic trees under world body
   int nM;                         // number of non-zeros in sparse inertia matrix
   int nB;                         // number of non-zeros in sparse body-dof matrix
   int nC;                         // number of non-zeros in sparse reduced dof-dof matrix
@@ -722,7 +723,6 @@ struct mjModel_ {
   // sizes set after mjModel construction
   int nnames_map;                 // number of slots in the names hash map
   int nJmom;                      // number of non-zeros in sparse actuator_moment matrix
-  int ntree;                      // number of kinematic trees under world body
   int ngravcomp;                  // number of bodies with nonzero gravcomp
   int nemax;                      // number of potential equality-constraint rows
   int njmax;                      // number of available rows in constraint Jacobian (legacy)

include/mujoco/mjxmacro.h

@@ -77,6 +77,7 @@
     X( nbvhdynamic )        \
     X( noct )               \
     X( njnt )               \
+    X( ntree )              \
     X( nM )                 \
     X( nB )                 \
     X( nC )                 \
@@ -143,7 +144,6 @@
     X( npaths )             \
     X( nnames_map )         \
     X( nJmom )              \
-    X( ntree )              \
     X( ngravcomp )          \
     X( nemax )              \
     X( njmax )              \