[CI] TestCagraToHnswSerializationAndSearch flaky #2735

Summary

TestCagraToHnswSerializationAndSearch.testCagraToHnswSerializationAndSearch intermittently returns incomplete search results.

Failures

• Sep 29 nightly

  Id: 1608 expected but not found

• Oct 2 PR run

  Id: 320 expected but not found

The failures occurred on unrelated revisions and different architectures, suggesting this is flaky rather than change-specific.

Expected behavior

All expected IDs should be present consistently.