host: preserve bundle symlinks and finish integration test isolation

host/tests/it/hook.rs

@@ -1,6 +1,11 @@
 //! Real guest HTTP requests pass through caller identity, credential injection, and streaming transport.
-#[path = "hook_git.rs"]
-mod hook_git;
+mod hook_git {
+    //! Preserve the Git push registration that also ran inside the former hook executable.
+    #[tokio::test]
+    async fn several_mb_git_push() {
+        crate::hook_git::push().await;
+    }
+}
 use super::hook_guest;
 use sausage::{
     cred::{