RegressionMetrics rounds every metric to 2 decimals (documented in
lib.md); the old test compared against unrounded closed-form values
with a 1e-6 tolerance, which the rewritten activity can no longer
satisfy. Round the expected values the same way before comparing.
Confirmed via real Docker-backed Postgres/MinIO/Mongo + Temporal test
environment: all 4 simple_metrics e2e scenarios pass.
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