Change mj_ray behaviour to match geom visualisation conventions:

- Planes and height-fields respect `mj_ray`'s `geom_group` argument.
- The `flg_static` argument now applies to all static geoms, not only those directly in the world body.

Before this change:
- Rays always intersected with height fields and planes, unless `flg_static` was set to 0.
- `flg_static` only applied to static geoms that were direct children of the world, but not geoms that were children of static bodies.

PiperOrigin-RevId: 534969091
Change-Id: I8dc7c320c63d6af95709b9f5e83a3c50e1c199fa

src/engine/engine_ray.c

@@ -82,15 +82,10 @@ static int ray_eliminate(const mjModel* m, const mjData* d, int geomid,
   }
 
   // static exclusion
-  if (!flg_static && m->geom_bodyid[geomid]==0) {
+  if (!flg_static && m->body_weldid[m->geom_bodyid[geomid]]==0) {
     return 1;
   }
 
-  // plane and hfield inclusion
-  if (m->geom_type[geomid]==mjGEOM_PLANE || m->geom_type[geomid]==mjGEOM_HFIELD) {
-    return 0;
-  }
-
   // no geomgroup inclusion
   if (!geomgroup) {
     return 0;