S00-020: Verify pinned Linux XMPP toolchain restoration

Changes: Refresh the environment-access result and document S00-020 restoration, accepted prerequisites and independent QA handoff; preserve probe code and parent dependency graph.
Validation: verify.py passed official HTTPS vendor checksum, Node 24.21.0/npm 11.19.0, fresh-cache strict npm ci and Stanza import. Separate artifact/input/version/strict-setting assertions and tasks.py validate passed. No browser/WSS or product readiness check performed.

Task: S00-020
Agent: auto-ci-cd-2a0186c54ce9
Role: ci-cd
Action: claim
Status: review

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

state/tasks.json

@@ -1,6 +1,6 @@
 {
   "schema_version": 1,
-  "revision": 83,
+  "revision": 85,
   "tasks": {
     "S00-001": {
       "status": "done",
@@ -1282,18 +1282,19 @@
       "completed_at": "2026-10-14T19:52:28+00:00"
     },
     "S00-020": {
-      "status": "todo",
-      "owner": null,
+      "status": "review",
+      "owner": "auto-ci-cd-2a0186c54ce9",
       "external_wait": false,
       "reason": null,
-      "started_at": "2026-10-15T07:27:20+00:00",
-      "updated_at": "2026-10-15T10:04:38+00:00",
+      "started_at": "2026-10-15T10:04:44+00:00",
+      "updated_at": "2026-10-15T10:07:10+00:00",
       "blocked_by": [],
       "resume_status": "in_progress",
       "blocker_report": "state/blockers/S00-024.md",
       "handoff": "state/handoffs/S00-020.md",
       "previous_owner": "auto-ci-cd-5a18c8aa1b42",
-      "resumed_after_blocker": true
+      "resumed_after_blocker": true,
+      "evidence": "state/evidence/S00-020-auto-ci-cd-2a0186c54ce9.md"
     },
     "S00-021": {
       "status": "done",
@@ -2440,6 +2441,29 @@
       "to": "done",
       "reason": null,
       "evidence": "state/evidence/S00-024-review.md"
+    },
+    {
+      "revision": 84,
+      "at": "2026-10-15T10:04:44+00:00",
+      "action": "claim",
+      "task": "S00-020",
+      "agent": "auto-ci-cd-2a0186c54ce9",
+      "role": "ci-cd",
+      "from": "todo",
+      "to": "in_progress",
+      "reason": null
+    },
+    {
+      "revision": 85,
+      "at": "2026-10-15T10:07:10+00:00",
+      "action": "submit",
+      "task": "S00-020",
+      "agent": "auto-ci-cd-2a0186c54ce9",
+      "role": null,
+      "from": "in_progress",
+      "to": "review",
+      "reason": null,
+      "evidence": "state/evidence/S00-020-auto-ci-cd-2a0186c54ce9.md"
     }
   ],
   "retired_agents": [