test(09-05): add failing tests for deterministic bulk delete

- Empty selections are 422 and duplicates run once in primary-key order
- A completed retry and an all-absent selection delete nothing and skip hooks
- Mixed, hook, cancel, and concurrent requests keep the batch atomic

cabana/http.go

@@ -241,6 +241,10 @@ func (s *service) update(w http.ResponseWriter, r *http.Request) {
 	})
 }
 
+func (s *service) bulkDelete(w http.ResponseWriter, r *http.Request) {
+	WriteError(w, http.StatusInternalServerError, "error", msgServerError)
+}
+
 func (s *service) deleteRecord(w http.ResponseWriter, r *http.Request) {
 	s.protect(w, r, func(cc *CompiledController) {
 		id, err := pathID(r)