Summary

WT-18045 made test/format automatically disable ops.prepare and ops.truncate whenever disagg.stepdown_async is enabled (in config_disagg_storage(), test/format/format_config.c), warning if either was set explicitly. Neither operation is accounted for by the async step-down drain, so either could straddle step_down_ts and break the checkpoint's boundary guarantee - this is now enforced in code rather than left to task configuration.

Several Evergreen task configs in test/evergreen.yml still pass ops.prepare=0 ops.truncate=0 explicitly alongside disagg.stepdown_async=1. These are now redundant and, because they're explicit, will trigger a WARN message on every run.

Proposed change

Remove ops.prepare=0 ops.truncate=0 from every disagg.stepdown_async=1 task in test/evergreen.yml (currently 8 occurrences, both in format_test_script_args and format_args fields), relying on the automatic override added in WT-18045.

Expected outcome

Evergreen stepdown-async tasks no longer carry redundant config, and no longer emit the "turning off ops.prepare/ops.truncate" WARNING on every run.