yitayningwut
The stirah in rashi – i looked at rashi there again. You’re right, its not a stirah. I understood the words “gzeirah mishum ksus lailah” to mean gzeirah that he might forget to take off the sdinin before nightfall, which would imply like the Rambam. But i checked again in rashi, and that is not the way he explains it.
About pajamas – in the first definition that i set out in the earlier post, i said that ksus lailah is anything that is ‘made’ to be worn at night. So then it could be that it doesn’t go by the individual, but rather by the maker.
This doesn’t have to do with hazmanah or lishmah or anything like that. It is just a sevara in the concept of ksus lailah itself.
But you can definitely argue and say that a ksus lailah is something that is worn by night, regardless of what kind of beged it really is.