Foundation lib for v1.12.0 cron rewrite. Atomic exclusive create via
fs.writeFileSync('wx'); on EEXIST resolves staleness with OR semantics:
stale if PID is dead OR mtime exceeds threshold. Either alone breaks the
lock — handles SIGKILL orphans (mtime), PID-reuse races (mtime), and
crashed-then-replaced runs (PID).
- acquireLock(lockPath, opts) → {lockPath, release()}
- staleThresholdMs default 1h; refreshIntervalMs opt-in for long runs
- registerCleanup default true (exit/SIGINT/SIGTERM/SIGHUP/uncaughtException)
- isPidAlive uses kill(pid, 0) with EPERM-as-alive nuance
12/12 tests pass: PID liveness, fixture concurrency, idempotent release,
stale variants (dead+old, live+old, fresh+live), staleThresholdMs honored.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
