fix(gateway,cron): close ephemeral agents + reap stale aux clients (salvage #13979) (#16598)

* fix: clean gateway auxiliary client caches on teardown

* fix(gateway): recover from stale pid files and close cron agents

Two issues were keeping the gateway from surviving long runs:

1. `_cleanup_invalid_pid_path` delegated to `remove_pid_file`, which
   refuses to unlink when the file's pid differs from our own. That
   safety check exists for the --replace atexit handoff, but it also
   applied to stale-record cleanup, so after a crashy exit the pid
   file was orphaned: `write_pid_file()`'s O_EXCL create then failed
   with `FileExistsError`, and systemd looped on "PID file race lost
   to another gateway instance". Unlink unconditionally from this
   helper since the caller has already verified the record is dead.

2. The cron scheduler never closed the ephemeral `AIAgent` it creates
   per tick, and never swept the process-global auxiliary-client
   cache. Over days of 10-minute ticks this leaked subprocesses and
   async httpx transports until the gateway hit EMFILE. Release the
   agent and call `cleanup_stale_async_clients()` in `run_job`'s
   outer `finally`, matching the gateway's own per-turn cleanup.

* chore(release): map bloodcarter@gmail.com -> bloodcarter

---------

Co-authored-by: bloodcarter <bloodcarter@gmail.com>

scripts/release.py

@@ -63,6 +63,7 @@ AUTHOR_MAP = {
     "yoimexex@gmail.com": "Yoimex",
     "6548898+romanornr@users.noreply.github.com": "romanornr",
     "foxion37@gmail.com": "foxion37",
+    "bloodcarter@gmail.com": "bloodcarter",
     # contributors (from noreply pattern)
     "david.vv@icloud.com": "davidvv",
     "wangqiang@wangqiangdeMac-mini.local": "xiaoqiang243",