test(benchmarks): tag tasks as small change, larger implementation, or search

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

scripts/benchmarks/tasks/12-search-transient-retry/task.json

@@ -1,4 +1,5 @@
 {
+  "category": "search",
   "prompt": "Uploads that fail with a temporary network error are never retried. Make at most three attempts in total before giving up with the last error; other errors must not be retried.",
   "generate": {
     "filler_modules": 250