test: let the shared Vitest isolation win over a project's own options

[thymikee]

Summary

Follow-up to #3206. TEST_ISOLATION now spreads after each Vitest project's own test block, as the mutation lane already does, so no project can turn unstubEnvs off. This resolves the open P3 review thread on #3206. One line in vitest.config.ts.

Validation

At the pushed head: pnpm check:affected --run passes. A throwaway probe confirmed that a stub made in one test is gone in the next.

[cubic-dev-ai]

No issues found across 1 file

_{Re-trigger cubic}

[github-actions]

Size Report

Metric	Base	Current	Diff
Installed (including dependencies)	5.04 MB	5.04 MB	0 B
Package (unpacked)	5.04 MB	5.04 MB	0 B
Package (download)	1.51 MB	1.51 MB	-9 B

Startup median (7 runs, lower is better):

Scenario	Base	Current	Diff
CLI --version	26.0 ms	26.5 ms	+0.5 ms
CLI --help	75.3 ms	76.9 ms	+1.5 ms

[thymikee]

Code looks good at f74c38b. The change only touches the Vitest config, and the shared isolation setting now wins over a project's own options. All checks are passing and there are no conflicts. I did not run the test suite, and I did not find a regression test for the override order, since only the config line changed. Nothing else stands in the way of merge.

[github-actions]

PR Preview Action v1.8.1
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2026-10-05 05:48 UTC