brokerd: ask_memory, a built-in memory tool that memoryd runs

Co-Authored-By: ornith-1.5-35b-a3b <agent@wntrmute.dev>

crates/brokerd/tests/grants.rs

@@ -95,7 +95,7 @@ fn an_empty_directory_is_a_valid_empty_set() {
     let builtin: Vec<&str> = set.matchable().map(|g| g.id.as_str()).collect();
     assert_eq!(
         builtin,
-        ["builtin-memory", "builtin-recall"],
+        ["builtin-memory", "builtin-recall", "builtin-ask-memory"],
         "only the built-ins"
     );
 }