test: apply a delay to watch-mode-kill-sginal tests

[joyeecheung]

The test is still flaking on macOS. This might be caused by fs event coalescing. Apply a delay to reduce the chance of it. Also, add a bit more logs to show more information.

Refs: https://github.com/nodejs/reliability/blob/main/reports/2025-11-07.md

[joyeecheung]

I wonder if this might be a caveat of --watch in general, which seems to be using fs.watch and therefore risks the caveat of fsevents on macOS...not sure if it's ever considered to support something like --watch-poll for precision.

[joyeecheung]

I am not 100% sure that this would eliminate the effect of coalescing for this test - another option is to, er, write a few more times and cross fingers that they get picked by the fsevent-based watcher? But multiple writes could again lead to the tricky loop we wanted to avoid in #60443. So for now I guess we can just try the timeout and hopefully that is good enough..

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.56%. Comparing base (be3fc1f) to head (d0bba5a).
⚠️ Report is 30 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff            @@
##             main   #60610    +/-   ##
========================================
  Coverage   88.55%   88.56%            
========================================
  Files         704      704            
  Lines      207981   208099   +118     
  Branches    40068    40090    +22     
========================================
+ Hits       184187   184311   +124     
- Misses      15812    15824    +12     
+ Partials     7982     7964    -18     

see 39 files with indirect coverage changes

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[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/70089/