Changes made for Pathfinder 5226 controllers.

New setup parameter, struct field, and error code E478.

Check_BackGauge_2_Separation() runs every 1 ms from the run wait loop. It tolerates being outside the limit while the gap is closing or holding, and faults only if the gap opens further by more than BG2 tolerance. On fault it halts and stops both backgauges. Auto mode: Axis_Move_Conflict rejects a BG2 move whose intended target would exceed the limit. Jog mode: the jog target is clamped to the other backgauge plus or minus the limit, and a jog that would open the gap further is refused with E478.

Groups 1 and 2 share files and are only meaningful together, so they are effectively one checkin.