Fix sitting motion and remove spasms

[oxkitsune]

What

• Robot now correctly maintains its state when starting yggdrasil. E.g. it will keep standing instead of sitting down.
• The sitting gait of the walking engine no longer makes the robot fall over when starting yggdrasil.
• The joint current optimizer is now also applied whilst the robot is sitting.
• The robot no longer spasms when yggdrasil is started.

[Copilot]

Copilot reviewed 16 out of 16 changed files in this pull request and generated 1 comment.

Comments suppressed due to low confidence (2)

yggdrasil/src/motion/walking_engine/mod.rs:154

• The change from 0.8 to 0.0 for arm stiffness may introduce unintended behavior; please verify that setting arm stiffness to zero is intentional.

ArmJoints::fill(0.0),

yggdrasil/src/kinematics/mod.rs:176

• The adjustment in foot translation now adds 'ANKLE_TO_SOLE.z', which alters the computed foot position; please confirm that this change correctly reflects the intended physical model.

hip_height + dimensions::ANKLE_TO_SOLE.z