Windows has no POSIX parent-death supervisor/killpg safety net, so an
ungraceful exit of the hermes process left every stdio MCP child tree
(npx.cmd -> node.exe) running as orphans with ParentId=null, piling up
across session restarts.
- _run_stdio now attaches the process to a KILL_ON_JOB_CLOSE job object
before spawning stdio children (self-guarded no-op off Windows), so the
whole child tree dies with the parent at the kernel level.
- Windows reaps kill the process tree (direct child + descendants) in the
lifecycle orphan sweep and the spawn-ledger startup sweep, where there
is no pgid to group-kill.
Fixes#61059
0cd93f0268