refactor(kernel): split ipc/memory/lib/thread by concern; trim comments

crates/domain/src/generations.rs

@@ -6,9 +6,7 @@ use types::generation::Generation;
 #[path = "generations_tests.rs"]
 mod tests;
 
-/// A slot's generation changes every time the object in it is destroyed
-/// or revoked, so capabilities minted earlier stop matching. A slot whose
-/// counter runs out is retired for good rather than reused.
+/// Bumped on every destroy or revoke so older capabilities stop matching; a slot whose counter runs out is retired.
 pub struct SlotGenerations<const N: usize> {
     gens: [Option<Generation>; N],
 }