Much of the wiki information is out-of-date. You can’t craft the legendary weapons that are obtained from chests.
You can, however, craft some weapons that are considered legendary according to the grade displayed. Such as the Star Metal Spear, though the Flawless version is considered High Grade. This is likely just more incorrect descriptions.
Telith’s weapons are considered High Grade, not Legendary. Probably also incorrect descriptions as their damage really is on the legendary level, above it, actually. But they can be repaired without legendary repair kits, so who knows what these devs really want them to be.
As for repairing legendary weapons from chests, you need legendary repair kits. Only certain blacksmiths can create them. Those blacksmiths, as far as I know, come from purges.