## Summary
Fixes flaky CLI v3 E2E tests by removing fixture-level parallelism.
The suite was using `describe.concurrent`, but each fixture test mutates
its fixture workspace during setup: removing `node_modules`,
renaming/restoring lockfiles, and running package installs. On
Windows/npm this can race or hit file-lock/cache contention, causing
intermittent failures.
## Fix
Run the CLI v3 E2E fixtures serially instead of concurrently.
## Expected impact
This should make the Windows/npm E2E job more stable. The E2E step may
slow down from ~30s to roughly ~60–90s in typical runs, with a
conservative upper bound around ~2 minutes.
Chris Arderne
7851f5cad3