help it made the error go away but uhhhhhhhhhhhhh

"i have done a couple bad things"
help it made the error go away but uhhhhhhhhhhhhh
if it fits the interface and the types aren't set up properly for you to do const app: UnsafeAppInterface then yeah, do as unknown as T. it hurts but there isn't much choice.
yeah as @noa suggested, as unknown as T is basically the typescript equivalent of reinterpret_cast<T>, which is to say it's your way of telling the typechecker "okay, even if you don't know what this is, I know it's a T so stop bugging me"
the good news is that it's idiomatic enough that if it breaks, any other typescript developers who see it will immediately know what you were doing