S00-020: Record blocked task and remediation handoff

Changes: Preserve incomplete work and blocker metadata for S00-020. This checkpoint does not mark implementation accepted.
Validation: Session ended with status blocked.
Blocker: Previous runner session was interrupted before submit/escalate; processes stopped. User now explicitly requests resuming development. Preserve partial artifacts, verify them in a fresh bounded remediation, and return original to a new executor only after independent review.

Task: S00-020
Agent: auto-ci-cd-5a18c8aa1b42
Role: ci-cd
Action: claim
Status: blocked

Task title: Restore access to the pinned Linux XMPP experiment toolchain

planning/tasks.json

@@ -1137,7 +1137,8 @@
         "S00-002",
         "S00-017",
         "S00-018",
-        "S00-019"
+        "S00-019",
+        "S00-024"
       ],
       "requirements": [
         "ACC-004",
@@ -1328,6 +1329,58 @@
       ],
       "context_budget_chars": 48000
     },
+    {
+      "id": "S00-024",
+      "stage": "S00",
+      "kind": "blocker",
+      "root_task": "S00-003",
+      "blocker_depth": 2,
+      "unblocks": [
+        "S00-020"
+      ],
+      "role": "ci-cd",
+      "reviewer_role": "qa",
+      "title": "Устранить прерывание: Restore access to the pinned Linux XMPP experiment toolchain",
+      "outcome": "Устранить одну указанную причину прерывания и доказать готовность исходной задачи к новому запуску; не выполнять соседние задачи.",
+      "depends_on": [
+        "S00-001",
+        "S00-002",
+        "S00-017",
+        "S00-018",
+        "S00-019"
+      ],
+      "requirements": [],
+      "scope": [
+        "experiments/0002-xmpp-library/environment-access/**"
+      ],
+      "inputs": [
+        "docs/WEB_PROFILE.md",
+        "docs/ARCHITECTURE.md",
+        "docs/CONTRACTS.md",
+        "docs/TESTING.md",
+        "roles/protocol.md",
+        "docs/decisions/README.md",
+        "state/blockers/S00-020.md",
+        "state/blockers/S00-024.md"
+      ],
+      "spec_sections": [],
+      "ui_sections": [],
+      "steps": [
+        "Прочитать blocker report и handoff.",
+        "Воспроизвести конкретную причину.",
+        "Исправить только локальную причину в scope или уточнить внешний input.",
+        "Выполнить focused проверку и submit."
+      ],
+      "acceptance": [
+        "Причина воспроизводимо устранена.",
+        "Исходная задача не завершена обходом требований."
+      ],
+      "checks": [
+        "Повторить сценарий прерывания.",
+        "Проверить отсутствие изменений вне scope."
+      ],
+      "context_budget_chars": 48000
+    },
     {
       "id": "S00-010",
       "stage": "S00",