test: one test fails at random in the pre-push gate

Problem

pnpm run check failed three times in the pre-push hook during one session. Each failure reported
exactly one failed test. A rerun passed every time. CI never failed.

Observations

The name of the failed test was not captured. The second failure happened after
test/tools/metadata-merge.test.ts existed, the first one before it, so the flake is not limited to
one file.

Not reproducible on demand

The full suite passed 12 times in a row afterwards, both with and without coverage.
test/stdio.test.ts passed 8 times in a row on its own.

A likely cause

Vitest runs the files in parallel. Several tests start the real Quarto CLI, and one starts a child
Node process. A loaded machine makes those slower. The pre-push hook runs while the developer does
other work, which is the one condition that the clean runs did not have.

Next step

Capture the name first. Add a reporter that keeps the failure, for example
vitest run --reporter=junit --outputFile=..., or run the hook with --retry=0 --bail=1 and keep
the log. Fix nothing until the failing test is known.

Not a blocker

The v0.2.0 release passed the gate on Node 22 and Node 24.

Start with the pre-push hook and pnpm run check; rerun with --retry=0 --bail=1 while retaining the output, or use the suggested JUnit reporter. Review test/tools/metadata-merge.test.ts and test/stdio.test.ts as the named comparison points. Done means the randomly failing test is identified and the flake is addressed, with the check passing reliably.