feat(zone): don't spawn carver_only objects, keep them as walls

The client never loads a level object whose config has carver_only set (its
resource manager skips the load; LWOBasePhysComponent::LoadConfigData
0x00c495c9 reads the flag next to navmesh_carver), and live never sent one:
none of the 331 carver_only placements (mostly Crux Prime's trigger boxes)
shows up among the live constructions, where their zones' other objects do.
DLU spawned them as objects.

They are skipped now. The ones that carve the navmesh (53, in six zones,
among them the Avant Gardens Sentinel camp walls) still stop the server's movers: their shape
goes into the world's movement blockers without an object, owned by the
physics world (dpWorld::AddOwnedMovementBlocker) and freed when it shuts
down. None of them has a script, trigger or group.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

dPhysics/dpWorld.h

@@ -34,6 +34,11 @@ namespace dpWorld {
 	 * the caller, who removes it before deleting it; it is not stepped with the world.
 	 */
 	void AddMovementBlocker(const dpEntity* entity, uint32_t filter);
+	/**
+	 * A movement blocker with no object of its own (a wall from the level files the server doesn't spawn), owned by the
+	 * world from now on and freed when it shuts down.
+	 */
+	void AddOwnedMovementBlocker(dpEntity* entity, uint32_t filter);
 	void RemoveMovementBlocker(const dpEntity* entity);
 	std::span<const dpMovementBlocker> GetMovementBlockers();