feat(userspace): shell runs programs (ls, cat) via spawn w/ terminal+storage+args page; ext4 holes read as zeros; storage re-attach same buffer

crates/servers/storage-server/src/tests/server.rs

@@ -67,10 +67,14 @@ fn nothing_works_before_attaching() {
 }
 
 #[test]
-fn a_client_attaches_once() {
+fn attaching_again_hands_back_the_same_buffer() {
     let mut s = server();
-    Client::attach(&mut s, 0);
-    assert_eq!(call(&mut s, 0, StorageRequest::Attach).0, StorageResponse::Error);
+    let (first, cap) = call(&mut s, 0, StorageRequest::Attach);
+    assert_eq!(call(&mut s, 0, StorageRequest::Attach), (first, cap));
+    // Not a new client: the other seven places are still free.
+    for badge in 1..8 {
+        assert!(matches!(call(&mut s, badge, StorageRequest::Attach).0, StorageResponse::Attached { .. }));
+    }
 }
 
 #[test]