UnsteadyAero numerical improvements to UAMod 4-6

[bjonkman]

This PR is ready to be merged.

Feature or improvement description
This PR makes some numerical improvements to the continuous unsteady-aero states:

• It adjusts the way the states are treated when UA is turned off. When UA is turned off due to low relative velocity, the state derivatives are now weighted to zero instead of blending the states to the steady-state solution in the UpdateStates routine (which is what is done in the calcOutput routine).
• It refactors the equation for alphaE to deal with +/-180-degree jumps in alpha_34 compared to x1 or x2 states. This is similar to how the state derivatives already deal with the angle of attack subtraction from x1 and x2 states when calculating their derivatives.

These changes have resulted in smoother states and alphaE calculations.

Related issue, if one exists
None

Impacted areas of the software
Unsteady aero models that use the HGM-type continuous states: UAMod 4, 5, & 6

Generative AI usage
Assisted-by: Kiro:claude-opus-5.5

Test results, if applicable

• A couple of channels in the ad_BAR_SineMotion_UA4_DBEMT3 test fail. The newer results look smoother than the baseline: