test(temporal): tolerate completed update races

[gregkonush]

Summary

• Treats a workflow that completes naturally before or during update failure injection as a terminal load-test outcome.
• Preserves fatal behavior for unrelated update failures and limits transient cleanup suppression to the termination phase.
• Adds a focused regression that verifies an already-completed update race skips the termination call.

Related Issues

Prerequisite repair discovered while validating #12422.

Testing

• bun test packages/temporal-bun-sdk/tests/integration/load/runner.test.ts — 12 passed.
• tsc --noEmit --project packages/temporal-bun-sdk/tsconfig.json --pretty false — passed.
• git diff --check — passed.
• The integration-load directory is excluded by the repository’s Oxc ignore rules, so Oxfmt/Oxlint cannot target these files through the normal configuration.

Breaking Changes

None.

Checklist

• Testing section documents the exact validation performed and the Oxc exclusion.
• Screenshots are not applicable; Breaking Changes is filled in.
• The focused regression documents the intended load-harness race policy.