Prove in CI that Stryker scores a load-breaking mutant as killed #856

What happens

#852 makes Stryker count a test file that fails to load as a failed test, through a vitest reporter. The suite proves the reporter's transform and what a real vitest run hands a Stryker-style collection, but not the last step: that Stryker itself then scores the mutant Killed. Only the mutation scopes' scores show it, and only indirectly.

Stryker cannot be configured out of this. @stryker-mutator/vitest-runner 10.0.0, the latest release, still builds results from collected tests only (vitest-test-runner.js:171-172); its options are dir, related and configFile; ignoreStatic drops such mutants rather than killing them. So a runner or vitest upgrade that bypasses the reporter would bring the false survivors back silently.

Expected

A mutation scope whose only mutant stops a module from loading, with a floor of 100. If Stryker ever reports that mutant as anything but Killed, the scope fails. It runs whenever the harness changes, so on every Stryker or vitest upgrade.