feat(kernel): per-process budgets (pages, endpoints, notifs, regions) carved from creator, returned on death; init owns pool

crates/kernel/src/tests/captree_model.rs

@@ -163,6 +163,7 @@ impl World {
             Syscall::CreateProcess {
                 create_cap: CapSlot::new(0).unwrap(),
                 image: DataRef::empty(),
+                limits: super::helpers::CHILD_LIMITS,
             },
         );
         self.pids[i] = self.k.process_of_cap_for_test(cap);