DART 6.16.6

This is a patch release for the 6.16 LTS line, fixing warning spam and crash guards.

• Constraint

  • Fix slip compliance validation to silently handle the -1.0 sentinel value (meaning "use default") instead of logging spurious warnings: gz-sim#3289

• Dynamics

  • Guard against non-finite articulated body computations from zero/epsilon mass or extreme spring values: gz-physics#849, gz-physics#850, gz-physics#851, gz-physics#854, gz-physics#856