I said I would earlier in the thread so I went back and looked at how various sources detail the githyanki:
1e Fiend Folio - Psionics only appear in the stat block, and are not addressed in the flavor text. The flavor text briefly tells of their revolt against the mind flayers, split with the githzerai, and their having a lich queen (though she is not named), and their association with red dragons.
1e MotP - there's about a half page that talks about them. It spends most of that space talking about various mechanics related issues, class restrictions, changes to their stats from the Fiend Folio, and it references some 1e psionic powers. Of the fluff that is present, it mentions the them having a lich queen, living on fortresses on "islands of matter" in the astral, and their periodic raids against githyanki. The lich queen is not named.
2e Planescape Monstrous Compendium - For what it's worth, looking at the PSMC I, it doesn't discuss githyanki with psion levels, though it does discuss their use of "psychic and strange astral energies" principally among the Hr'a'cknir of githyanki society. The suggestion is there in the fluff, but it doesn't explicitely address anything related to the mechanics of 2e psionics (which I'm not admittedly familiar with). The 1e material is expanded by a good bit.
2e Guide to the Astral Plane - from pages 44-67, a whole chapter is devoted to the githyanki, their origins and history, society, social divisions and castes/classes, githyanki fotresses, tactics, unique magic, etc. Virtually all of their most unique traits and details originate in this souce, including as far as I can tell, for the first time calling the lich queen 'Vlaakith'. Psionicists are addressed, and approximately 75% of githyanki are considered wild talents while a significant fraction of those have actual training in the class. Such githyanki psions are normally referred to and treated as githyanki warlocks (arcane magic users, not the 3.x class).
3.x - the terminology introduced in the 2e sources is retained, along with Vlaakith being the name of the lich queen, along with the basics laid down in the 1e material and expanded in 2e. Psionics or not psionics alternates radically by source.