S00-003: Record blocked task and remediation handoff

Changes: Preserve incomplete work and blocker metadata for S00-003. This checkpoint does not mark implementation accepted.
Validation: Session ended with status blocked.
Blocker: S00-003 cannot reproduce accepted Node 24.21.0/npm 11.19.0 or install locked Stanza: host tools are 24.1.0/11.3.0, parent node_modules is absent, and normal official HTTPS retrieval fails with unresolved configured proxy.

Task: S00-003
Agent: auto-protocol-59f4d359b339
Role: protocol
Action: claim
Status: blocked

Task title: Проверить XMPP WSS/auth библиотеку

planning/tasks.json

@@ -270,7 +270,8 @@
         "S00-002",
         "S00-017",
         "S00-018",
-        "S00-019"
+        "S00-019",
+        "S00-020"
       ],
       "requirements": [
         "ACC-004",
@@ -1115,6 +1116,63 @@
       ],
       "context_budget_chars": 48000
     },
+    {
+      "id": "S00-020",
+      "stage": "S00",
+      "kind": "blocker",
+      "root_task": "S00-003",
+      "blocker_depth": 1,
+      "unblocks": [
+        "S00-003"
+      ],
+      "role": "ci-cd",
+      "reviewer_role": "qa",
+      "title": "Restore access to the pinned Linux XMPP experiment toolchain",
+      "outcome": "One independently reviewed environment-access probe demonstrates authentic pinned Linux Node/npm and integrity-verified installation of the parent locked dependency graph without changing accepted stack or network security policy.",
+      "depends_on": [
+        "S00-001",
+        "S00-002",
+        "S00-017",
+        "S00-018",
+        "S00-019"
+      ],
+      "requirements": [
+        "ACC-004",
+        "NET-003",
+        "NET-004"
+      ],
+      "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"
+      ],
+      "spec_sections": [],
+      "ui_sections": [],
+      "steps": [
+        "Read S00-003 blocker evidence and accepted stack pins.",
+        "Obtain external approved HTTPS connectivity or authentic locally supplied pinned Linux runtime and locked dependency artifacts.",
+        "Verify vendor checksum for runtime, exact node/npm versions, and lock integrity with a script confined to the remediation directory; install a copy of the parent manifest/lock only inside that directory.",
+        "Document reproducible approved artifact paths or connectivity and actual results; submit for independent review."
+      ],
+      "acceptance": [
+        "Node 24.21.0 and npm 11.19.0 execute on this Linux host with authenticated vendor checksum verification recorded.",
+        "Copied unchanged parent package-lock installs successfully with package integrity enforced and Stanza 12.22.1 available.",
+        "No stack/lock/spec changes, engine or TLS bypass, proxy policy bypass or secrets in evidence."
+      ],
+      "checks": [
+        "Exact runtime version and official checksum comparison.",
+        "Isolated npm ci of unchanged parent manifest/lock with lifecycle scripts disabled and TLS verification retained.",
+        "Independent review repeats access/runtime/lock checks."
+      ],
+      "context_budget_chars": 48000
+    },
     {
       "id": "S00-010",
       "stage": "S00",