S00-014: Make successful runner process-tree cleanup idempotent

Changes: Record completed termination on the Popen instance after all cleanup steps succeed; avoid repeated signals to the reaped group. Add deterministic repeated-EPERM and failed-descendant-kill retry regressions without suppressing permission errors.
Validation: Four focused cleanup tests passed; make check passed 72 tests and plan/snapshot validation. git diff --check passed. Natural prior EPERM did not recur; injected EPERM reproduced the pre-fix failure. No application or parent-task acceptance is claimed.

Task: S00-014
Agent: auto-ci-cd-14343249da62
Role: ci-cd
Action: claim
Status: review

Task title: Fix repeated runner cleanup after a submitted parent is reaped

planning/TASK_MATRIX.md

@@ -1,6 +1,6 @@
 # Матрица задач
 
-Generated; state revision **19**. Canonical status: state/tasks.json.
+Generated; state revision **21**. Canonical status: state/tasks.json.
 
 | ID | Этап | Оператор | Reviewer | Статус | Owner | Зависимости | Задача |
 | --- | --- | --- | --- | --- | --- | --- | --- |
@@ -16,7 +16,7 @@ Generated; state revision **19**. Canonical status: state/tasks.json.
 | [S00-011](tasks/S00-011.md) | S00 | ci-cd | security | done | auto-ci-cd-d105e8027730 | S00-001 | Restore verified npm registry access for the stack spike |
 | [S00-012](tasks/S00-012.md) | S00 | ci-cd | qa | blocked | auto-ci-cd-28868645424b | S00-001, S00-011, S00-013, S00-014 | Fix runner prompt delivery after partial stdin timeout |
 | [S00-013](tasks/S00-013.md) | S00 | ci-cd | qa | done | auto-ci-cd-5f68f03dd33b | S00-001, S00-011 | Bound oversized S21-006 runner context without truncating requirements |
-| [S00-014](tasks/S00-014.md) | S00 | ci-cd | qa | todo |  | S00-001, S00-011, S00-013 | Fix repeated runner cleanup after a submitted parent is reaped |
+| [S00-014](tasks/S00-014.md) | S00 | ci-cd | qa | review | auto-ci-cd-14343249da62 | S00-001, S00-011, S00-013 | Fix repeated runner cleanup after a submitted parent is reaped |
 | [S00-010](tasks/S00-010.md) | S00 | qa | orchestrator | todo |  | S00-001, S00-002, S00-003, S00-004, S00-005, S00-006, S00-007, S00-008, S00-009 | Gate: Профиль и проверка стека |
 | [S01-001](tasks/S01-001.md) | S01 | orchestrator | security | todo |  | S00-010 | Описать identity/model contracts |
 | [S01-002](tasks/S01-002.md) | S01 | orchestrator | security | todo |  | S00-010, S01-001 | Описать async account context |