fix(robotics): enable collider for mesh-bearing URDF collision links

[aki-xavier]

Problem

LoadBotPrefabFromUrdfFile fills shapeFile/shapeRotation/shapeTranslation/shapeScale for mesh-bearing <collision> geometry, but leaves colliderType at the prefab default (ColliderType::None). The resulting Bot has no collision representation at all:

• mochi contact queries on the actor are refused with the error "Contact queries are only supported for actors with contact sample points." (the prefab default leaves the colliders off, so no contact sample points are generated);
• no contact is produced against other actors, so contact force/torque reads and contact-aware controllers see a contactless robot.

Change

When a URDF <collision> mesh resolves on disk, set link->colliderType = ColliderType::Auto so the link participates in contact. Links without a mesh collision (or with only primitive geometry) keep the prefab default and remain untouched.

This mirrors what the old importer's mesh-based collision path was meant to do, and is required for both mochi's contact queries and the contact simulation itself.

Tests

Added to urdf_mesh_resolution_test.cpp:

• MeshCollisionEnablesColliderType — mesh <collision> → shapeFile set and colliderType == Auto;
• PrimitiveCollisionKeepsDefaultColliderType — primitive-only <collision> → shapeFile empty and colliderType == None (unchanged default).

Verification (point of failure → after)

Using a 6-DOF arm URDF whose collision meshes are STL meshes: before the fix every link reports colliderType=0 (None) and RegisterQuery(QueryType::TotalContactForce) fails for all links; after the fix, mesh-bearing links report a real collider (resolved to the SDF collider), contact queries register, and a wall-push experiment produces a real contact wrench (bounded, stable contact force scaling with controller stiffness).

Note: the importer's existing behavior of skipping primitive <collision> geometry (boxes/cylinders/spheres) is unchanged — such links still get no collider, which is why a URDF whose collisions are all primitives must be given mesh collisions (or the importer extended later) to become contact-enabled.

[meta-cla]

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[epezentFB]

@aki-xavier Can you help me understand the problem a bit better? I'm not sure this is fixing a bug:

1. Tracing the lineage of BotLinkPrefab::colliderType takes us to ArticulatedLinkParams where it is Auto:
   

   project_superdex/superdex_physics/libraries/mochi/mochi_physics/include/mochi_physics/cpp_api/mochi_structs.h

   Line 223 in 8706a8c

   ColliderType colliderType = ColliderType::Auto;

2. If I import a URDF into SuperDex Studio, mesh bearing links have Auto for collision:

[epezentFB]

Could you please also share the URDF if possible?