backport: non-blocking stdin quit monitoring

[MilesCranmerBot]

Backport of #562 to release-v1.

Includes the fast unit reproducer + non-blocking stdin quit monitoring fix.

[codecov]

Codecov Report

❌ Patch coverage is 85.71429% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.81%. Comparing base (c85c1ac) to head (6297684).
⚠️ Report is 2 commits behind head on release-v1.

Files with missing lines	Patch %	Lines
src/SearchUtils.jl	85.71%	4 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff               @@
##           release-v1     #563      +/-   ##
==============================================
+ Coverage       92.61%   92.81%   +0.19%     
==============================================
  Files              41       41              
  Lines            3655     3673      +18     
==============================================
+ Hits             3385     3409      +24     
+ Misses            270      264       -6     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.