* fix(mcp): settle local harness process trees

* fix(swe-arena): isolate cells and settle workers

* fix(lifecycle): close remaining cleanup races

* fix(lifecycle): fail closed on interrupted evaluations

* fix(swe-arena): settle workers on terminal failure

* test(swe-arena): isolate ambient OpenCode fixture

* test(swe-arena): stub auth command in isolation test

* test(swe-arena): stub OpenCode path probe