- Added `Process` class with pidfd (Linux), libproc (macOS), and handle (Windows) ownership for race-free signaling.
- Replaced `killTree`/`listDescendants` free functions with `Process.fromPid`, `fromPath`, `terminate`, and `waitForExit`.
- Added `TerminationTargets` for batching pgid+pid sets across pty and shell job teardown.
- Migrated `procmgr` and `ptree` to use the new native API, removing the `setNativeKillTree` injection pattern.