Use G59.3 As TLR - tool length reference

[LoganFraser]

Basically add an option to use the G59.3 directly as the TLR - Tool length reference. That way it's persistent between resets, and tools are measured compared to a static machine space point.

I don't know if this is a grblhal core thing or if it could just be set within iosender as T98 or something (since T99 is often used for 3d probe)