"You are sleeping."
Translation:Tá tú i do chodladh.
A quick note for anybody who stumbled across this. For passive actions or states, Irish uses the construction 'i [possessive] [verbal noun]'.
Sleeping is an example of this, as is sitting. However, if you're in the process of going from a standing state to a sitting state, you'd use 'ag', though once you're sitting, you'd use this construction.
If you think about it, they have to agree like that. The 'i' construction in this case literally translates into English as 'in your sleeping'. Thus the subject has to be 'you' (tú), or it wouldn't make any sense: you couldn't say 'I am in your sleeping', or 'she is in his sleeping' as that would imply that two parties are in exactly the same state of sleep, thus the subject of the sentence and the possessor of the state have to agree.
No, it's how Irish expresses a state of being - I prefer the translation "I'm asleep", but English uses a present progressive construction in this case, and other examples don't have an "a-" version anymore.
"I was sitting there" - bhí mé i mo shuí ansin
"She is living in Waterford" - Tá sí ina cónaí i bPort Lairge
"We have been friends for ages" - táimid inár gcairde le fada
"when I was a boy" - nuair a bhí mé i mo ghasúr
No. Unqualified, "you are sleeping" means "you are asleep" which can only be expressed as tá tú i do chodladh.
tá tú ag codladh on its own would be béarlachas. You can say tá tú ag codladh i bpuball - "You are sleeping in a tent", where the habitual aspect makes more sense.