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

experiments/0002-xmpp-library/environment-access/result.json

@@ -7,8 +7,8 @@
     "node": "v24.21.0",
     "npm": "11.19.0"
   },
-  "runtime_bin": "/tmp/luma-S00-026-mil9mnes/node-v24.21.0-linux-x64/bin",
-  "cache": "/tmp/luma-S00-026-mil9mnes/npm-cache",
+  "runtime_bin": "/tmp/luma-S00-026-g156ah2_/node-v24.21.0-linux-x64/bin",
+  "cache": "/tmp/luma-S00-026-g156ah2_/npm-cache",
   "parent_sha256": {
     "package.json": "e0ffb0c94e198e26f8e44e9b22ff4e121760d9f1197ed7bd5a90e1b4bb112766",
     "package-lock.json": "9c85ad62721eb2deacb298f29fa2bae211a29c964707d52c2dfbf8614b7dbb05"