v0.2.0

Four process-lifetime fixes asked for by Genie 2.0.0-beta.33. Every one is
proven by test/live/lifecycle.live.mjs on real CI runners. That suite was red
against 0.1.4 first and is green with these fixes.

Changed

• BEHAVIOUR CHANGE: a pty now dies with the process that opened it. If the
  controlling process exits, crashes or is killed outright, every helper it
  owned hard-kills its whole tree and exits. On Windows the job object is
  terminated at once. On POSIX the process group gets SIGHUP, up to 250 ms to
  leave, then SIGKILL. Before this, on Linux and macOS, every pty and
  everything it started kept running with nobody left to read or stop it, so a
  restarted app started duplicates. CI measured 10 helpers, 10 children and 10
  grandchildren all still alive 2 s after the controller was SIGKILLed on
  0.1.4. Now it is 0 / 0 / 0 on all four live platforms.

  What you must DO: nothing, unless you relied on terminals surviving the
  process that opened them. There was never a supported detached mode, so
  that only ever worked by accident, and only on POSIX. If you want terminals
  to outlive your UI, open them from a long-lived host process, as
  fancy-term-host's pty host already does. That host stays their controller,
  so this change does not affect it.

  On Windows the old behaviour was already this one, but only by accident.
  CI measured 0 survivors on 0.1.4 there, because a Node controller put the
  helper in libuv's kill-on-close job. Spawning the helper detached (next entry)
  removes that, and the helper now does it itself.

• Windows: the helper no longer has a console of its own. It is spawned
  detached (DETACHED_PROCESS) instead of with a hidden console, which saves
  one conhost.exe (about 8 MB) per pty. Measured in CI: 2 conhosts per helper
  on 0.1.4, 1 now (the pseudoconsole's own). Nothing to do. The helper's stdio
  is still the three pipes, and no console window can appear.

Added

• pty.childPid: the pid of the command itself (argv[0]), sent by the
  helper right after the command is created and before its first output. So it
  is set by the first onData, and stays undefined if the command never
  started. pty.pid is unchanged: it is still the helper's pid, and
  killing it still takes the whole tree.

• pty.kill({ graceMs }), a graceful stop. On Windows it types Ctrl-C into
  the console. On POSIX it sends SIGTERM to the process group. If the whole
  tree, grandchildren included, has not exited within graceMs, it is
  hard-killed. pty.killedBy ("graceful" | "forced" | null) and a
  new second argument to onExit, { killedBy }, report which happened.
  kill() with no argument is unchanged: an immediate hard kill, now reported
  as "forced". Existing onExit(code => …) listeners keep working. Note
  that an interactive shell at its prompt ignores both Ctrl-C and SIGTERM, so
  a bare shell always ends "forced". The graceful path is for the workers
  running inside it.

  "graceful" means the tree exited by itself after the polite signal. It
  does not mean the program finished its work. Whether Ctrl-C or SIGTERM
  lets a job complete is up to the program. One case worth checking before you
  rely on it: PHP on Windows has no pcntl, and as far as we know Laravel's
  queue:work cannot trap Ctrl-C there, so it would stop mid-job and still be
  reported "graceful". That is not measured. On POSIX, queue:work treats
  SIGTERM as "finish the current job, then stop".

• Protocol: a PID frame (0x84), a KILLED frame (0x85), and an optional
  [graceMs u32] payload on KILL. See native/proto.md. The empty KILL is
  the 0.1.x frame and keeps its meaning.

Fixed

• Windows: a process the command starts in its first instant can no longer
  escape the tree kill. The command used to be assigned to the job object
  only after it had started running. Anything it launched in that window was
  born outside the job, so neither kill() nor the helper's death could reach
  it. It is now created suspended, assigned, then resumed. The window was too
  narrow to hit on demand, so the test holds it open with a test-only helper
  setting (FANCY_PTY_TEST_ONLY_ASSIGN_DELAY_MS): red on 0.1.4, green now.
  Only a descendant that is not attached to the pseudoconsole could escape.
  One that stays on the console dies when the console closes anyway, which the
  first red run showed.