What bird is this seen trekking in Nepal during descent on Manaslu circuit?
You found an Alpine accentor (Prunella collaris). It's a bird of mountain areas in the Paleartic.

Here is a picture for comparison: 



The only similar bird in the area is the Altai accentor (Prunella himalayana), but you can tell it apart because your bird does not have streaked flanks and the more uniform grey head (in your picture it is clearly visible the supercilium)