worker: fix TOCTOU race in CWD caching

[mcollina]

The atomic counter used to signal CWD changes to worker threads was
being incremented before chdir() completed, creating a race window
where workers could cache stale directory paths with the new counter
value. This caused process.cwd() in workers to return incorrect values
until the next chdir() call.

Fix by reordering operations: call originalChdir() first, then
increment the counter. This ensures workers never cache stale data
while believing it is current.

A unit test for this fix is not feasible as it would be too flaky due to the timing-dependent nature of the race condition.

Reported-by: Giulio Comi
Reported-by: Caleb Everett

[mcollina]

cc @nodejs/tsc

[Renegade334]

FYI, a PR was opened by the community reporter at #61664.

[anonrig]

Nice catch.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.75%. Comparing base (81e05e1) to head (4b045af).
⚠️ Report is 357 commits behind head on main.

Additional details and impacted files

@@ Coverage Diff @@## main #61725 +/- ##
==========================================
+ Coverage 88.53% 89.75% +1.21% 
==========================================
Files 703 675 -28 Lines 208538 204525 -4013 Branches 40224 39306 -918 ==========================================
- Hits 184629 183565 -1064 + Misses 15912 13241 -2671 + Partials 7997 7719 -278 

Files with missing lines	Coverage Δ
lib/internal/worker.js	96.52% <100.00%> (ø)

... and 199 files with indirect coverage changes

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