Add geom adhesion: contacts that pull, via translated friction cones.

https://youtu.be/GioWwB36XHI

The new geom attribute adhesion (units of force, signed; pair-level
override) translates the contact friction cone along its normal so
that the force origin lies strictly inside it. Consequences: each
contact can pull with up to the given force before breaking, and the
tangential friction budget becomes mu*(f_N + adhesion) -- the
Mohr-Coulomb yield condition with cohesion c = mu*adhesion -- so
lightly-squeezed grasps retain a guaranteed friction floor.

A translated cone factors exactly into {constant attractive force}
+ {original cone}, so no solver kernels change. The implementation is
this factorization: a constant attraction along contact normals
accumulated into the new mjData.qfrc_adhesion (summed into
qfrc_passive), plus a bias of adhesive contact rows' reference
acceleration (aref += R*adhesion), which makes resting penetration
exactly independent of adhesion. Contacts of adhesive pairs remain
active throughout the gap zone, producing rows with positive violation
whose reference acceleration pulls: a tether that resists pull-off
smoothly, captures objects released within the band into steady
contact, and detaches at the specified force. Adhesion values of the
two geoms combine by sum; explicit pairs override.

mj_contactForce reports the net interface force (cone force minus the
adhesive pull), whose normal component can now be negative. Negative
adhesion is allowed and produces a repulsive offset (air hockey).

PiperOrigin-RevId: 950858148
Change-Id: I879c08eba7ae501e5c0f8c2f807167344da4c2bc

wasm/codegen/generated/bindings.h

@@ -377,6 +377,12 @@ struct MjContact {
   emscripten::val solimp() const {
     return emscripten::val(emscripten::typed_memory_view(5, ptr_->solimp));
   }
+  mjtNum adhesion() const {
+    return ptr_->adhesion;
+  }
+  void set_adhesion(mjtNum value) {
+    ptr_->adhesion = value;
+  }
   mjtNum mu() const {
     return ptr_->mu;
   }
@@ -3091,6 +3097,12 @@ struct MjsPair {
   void set_gap(double value) {
     ptr_->gap = value;
   }
+  double adhesion() const {
+    return ptr_->adhesion;
+  }
+  void set_adhesion(double value) {
+    ptr_->adhesion = value;
+  }
   emscripten::val friction() const {
     return emscripten::val(emscripten::typed_memory_view(5, ptr_->friction));
   }
@@ -4320,6 +4332,12 @@ struct MjModel {
   void set_flg_surfacevel(mjtBool value) {
     ptr_->flg_surfacevel = value;
   }
+  mjtBool flg_adhesion() const {
+    return ptr_->flg_adhesion;
+  }
+  void set_flg_adhesion(mjtBool value) {
+    ptr_->flg_adhesion = value;
+  }
   emscripten::val buffer() const {
     return emscripten::val(emscripten::typed_memory_view(ptr_->nbuffer, static_cast<uint8_t*>(ptr_->buffer)));
   }
@@ -4626,6 +4644,9 @@ struct MjModel {
   emscripten::val geom_surfacevel() const {
     return emscripten::val(emscripten::typed_memory_view(ptr_->ngeom * 6, ptr_->geom_surfacevel));
   }
+  emscripten::val geom_adhesion() const {
+    return emscripten::val(emscripten::typed_memory_view(ptr_->ngeom, ptr_->geom_adhesion));
+  }
   emscripten::val geom_fluid() const {
     return emscripten::val(emscripten::typed_memory_view(ptr_->ngeom * mjNFLUID, ptr_->geom_fluid));
   }
@@ -5289,6 +5310,9 @@ struct MjModel {
   emscripten::val pair_gap() const {
     return emscripten::val(emscripten::typed_memory_view(ptr_->npair, ptr_->pair_gap));
   }
+  emscripten::val pair_adhesion() const {
+    return emscripten::val(emscripten::typed_memory_view(ptr_->npair, ptr_->pair_adhesion));
+  }
   emscripten::val pair_friction() const {
     return emscripten::val(emscripten::typed_memory_view(ptr_->npair * 5, ptr_->pair_friction));
   }
@@ -6290,6 +6314,12 @@ struct MjsGeom {
   emscripten::val surfacevel() const {
     return emscripten::val(emscripten::typed_memory_view(6, ptr_->surfacevel));
   }
+  double adhesion() const {
+    return ptr_->adhesion;
+  }
+  void set_adhesion(double value) {
+    ptr_->adhesion = value;
+  }
   double mass() const {
     return ptr_->mass;
   }
@@ -7055,6 +7085,9 @@ struct MjData {
   emscripten::val qfrc_fluid() const {
     return emscripten::val(emscripten::typed_memory_view(model->nv, ptr_->qfrc_fluid));
   }
+  emscripten::val qfrc_adhesion() const {
+    return emscripten::val(emscripten::typed_memory_view(model->nv, ptr_->qfrc_adhesion));
+  }
   emscripten::val qfrc_passive() const {
     return emscripten::val(emscripten::typed_memory_view(model->nv, ptr_->qfrc_passive));
   }