Foundation lib for status-fil + lock-fil writes in v1.12.0 cron rewrite.
Pattern: writeFileSync to <path>.tmp.<pid>.<random> then renameSync to
target. Defends against half-written files; readers either see the
previous version or the new one, never a partial.
- atomicWriteSync(path, content) — string or Buffer
- atomicWriteJson(path, obj) — 2-space indent, trailing newline
- Windows EEXIST/EPERM defensive fallback (unlink target + rename)
- Best-effort tmp cleanup on writeFileSync failure
- crypto.randomInt(0, 2**32) two-arg form (unambiguous across Node)
9/9 tests pass including 50-way concurrent-write fuzzer (async-aware
withTmp helper).
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
