fix: end a build whose output report has nowhere to go

[alexander-akait]

Summary

writeOutputFile guards against a compiler with no outputFileSystem:

new Promise((finish, bail) => {
  if (!compiler.outputFileSystem) return;

The return leaves the promise unsettled. What awaits it is processAssets's own callback, through await Promise.all(...) over the outputReport writes — so the guard did not skip the write, it hung the build. No error, no report, no end. Confirmed by calling it with a compiler that has no file system: the promise is still pending after 1.5s.

It answers now, which is what the guard meant to do.

What kind of change does this PR introduce?

fix.

Did you add tests for your changes?

Yes — test/utils.test.js races the call against a timer and asserts it answered. Against unmodified src/ it fails with 'never answered'; a first version of it let the process exit instead, so the timer is no longer unref'd and the regression fails rather than cancelling the suite.

Does this PR introduce a breaking change?

No.

If relevant, what needs to be documented once your changes are merged or what have you already documented?

n/a.

Use of AI

AI was used. It was asked for a small bug to exercise the release workflow with, picked this one out of an earlier audit, reproduced the unsettled promise before changing anything, and wrote the fix and the test.

🤖 Generated with Claude Code

https://claude.ai/code/session_01GzZci4NQeiqwdrVfd7dGXy

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Generated by Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.52%. Comparing base (af3f2b3) to head (10e099d).
⚠️ Report is 54 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #362      +/-   ##
==========================================
+ Coverage   98.69%   99.52%   +0.83%     
==========================================
  Files           6       17      +11     
  Lines         230     4252    +4022     
  Branches       65        0      -65     
==========================================
+ Hits          227     4232    +4005     
- Misses          3       20      +17     

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