fix(cli): keep child cleanup working on Windows

_cleanup_children() called os.killpg unconditionally — Windows doesn't
have killpg as an attribute on os, so the call raised AttributeError
(not caught by the existing OSError-family handler) and aborted cleanup.
Guard with hasattr(os, "killpg") and fall back to os.kill(pid, SIGTERM)
on platforms without process-group APIs. Closes #226. Refs #110.

Co-authored-by: gujishh <baiaoshh@163.com>

skills/last30days/scripts/last30days.py

@@ -63,7 +63,10 @@ def _cleanup_children() -> None:
         pids = list(_child_pids)
     for pid in pids:
         try:
-            os.killpg(os.getpgid(pid), signal.SIGTERM)
+            if hasattr(os, "killpg"):
+                os.killpg(os.getpgid(pid), signal.SIGTERM)
+            else:
+                os.kill(pid, signal.SIGTERM)
         except (ProcessLookupError, PermissionError, OSError):
             continue