Flaky: progress.test.ts worker-event forwarding fails under load #58

Test: forwards real workspace worker events without serializing the callback
File: packages/core/src/check/progress.test.ts

Observed:

• Failed once during the work on fix(fix): run a pinned Yarn Berry through corepack when the yarn on PATH is classic #54, while lint and build ran in parallel on the same machine.
• Passed 3 times in a row when run alone.
• Not seen in CI yet.

The test runs check() from the built packages/core/dist/index.js in a child process (execFileSync) against fixtures/repos/workspace-consumer. It then expects exactly ['start', 'done'] progress events for each workspace (., packages/app, packages/lib).

Next step: reproduce in a loop under CPU load and look for timing assumptions.