Ender Switchwire bed cable extension - full bed bracket + extension

use the mount hook from the original model.

my ender 3 v2 is a custom corexz conversion with a combination of custom designed parts, enderwire parts, switchwire parts, & parts from other corexz projects largely in the original v2 form factor - with some notable exceptions, the nonstandard bed carriage being most relevant here.  as such, this combination of concepts saved me space, among other considerations - many thanks to @LivingroomWorkbench for his original l design.