#131910 refused to signal a process group whenever its leader's start time
no longer matched the spawn-time baseline, and a REAPED leader reads as None,
so "leader gone" was treated as "PGID recycled". POSIX never reuses a PGID
while any member of the group lives, so a gone leader still leaves the group
ours, and its reparented grandchildren (an MCP server's pipe holder, a
terminal command's daemon) leaked past host shutdown.
Only a LIVE leader with a different start time (drift-tolerant since
a5e7df27) proves recycling now; the recycled-PID skip is unchanged.
a5e7df27 kept "gone leader refuses" and asserted it in
test_pgid_starttime_drift.py; that assertion now expects the kill. Same fix in the terminal
environment's twin guard (tools/environments/local.py::_leader_is_ours).
Red on main: tests/e2e/core/parity/test_mcp_lifecycle.py::
test_mcp_server_death_mid_call_fails_fast_and_the_turn_completes and
test_entrypoint_parity[*] zero_mcp_orphans (e2e lane on eaecc99c).
d526f14714