[FIX] Corrected limbs shift calculation in IKLimb.

[Neloreck]

Notes

• Treats an unreachable foot goal as a fully extended leg instead of allowing the square-root input to become negative.

Changes

• Clamps the IK leg-reach radicand before calculating the downward shift.
• Ignores non-finite upward and downward limb-shift constraints.
• Resets invalid persistent object_shift state and returns a zero shift.
• Logs IK shift-state recovery in debug builds.

Context

• Annoyed me since I compiled openxray first time.
• Verified with mixed build - skadovsk is good place to check it with ramps/stairs/doors etc.
• Removed verify, but added logs just in case. I think we can move it back to debug mode popup if anyone has preferences.