Stricter swapping condition in mju_eig3.

This solves the texture rendering issue with the Rubik's cube. The texture were specified with respect to the incorrect frame, so a default rotation of (0, 0, pi/2) is now applied to the model file.

PiperOrigin-RevId: 571715153
Change-Id: I3efae3b1fc8f64e6c9e4db90a7609506e3cbed86

src/engine/engine_util_solve.c

@@ -781,7 +781,8 @@ int mju_eig3(mjtNum eigval[3], mjtNum eigvec[9], mjtNum quat[4], const mjtNum ma
   for (int j=0; j < 3; j++) {
     int j1 = j%2;       // lead index
 
-    if (eigval[j1] < eigval[j1+1]) {
+    // only swap if the eigenvalues are different
+    if (eigval[j1]+eigEPS < eigval[j1+1]) {
       // swap eigenvalues
       t = eigval[j1];
       eigval[j1] = eigval[j1+1];