S00-020: Approve pinned Linux XMPP toolchain restoration

Changes: Accept S00-020 with independent QA evidence and handoff; refresh scoped runtime/cache result paths after fresh retrieval and installation.
Validation: verify.py passed official HTTPS checksum, Node 24.21.0/npm 11.19.0, isolated strict npm ci and Stanza import. Independent archive/input/eight-version/strict-setting assertions, tasks.py validate and diff/scope checks passed. Browser/WSS and product readiness remain untested.

Task: S00-020
Agent: auto-qa-9e1e289654ba
Role: qa
Action: review
Status: done

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

state/handoffs/S00-020.md

@@ -22,3 +22,14 @@ QA must independently rerun probe and inspect scope/strict flags/checksum/input
 bytes/installed versions before accepting S00-020. Coordinator alone commits and
 launches a fresh S00-003 executor after reviewed acceptance. This executor does
 not continue the parent task and exits immediately after submit.
+
+## Independent QA acceptance note
+
+Reviewer auto-qa-9e1e289654ba independently repeated verify.py successfully;
+see state/evidence/S00-020-review.md. Current result.json runtime is
+/tmp/luma-S00-026-j1pmys7w/node-v24.21.0-linux-x64/bin with sibling npm-cache.
+Official checksum, unchanged parent inputs, eight installed versions and strict
+settings passed independent checks. Approval accepts only S00-020 environment
+restoration. Coordinator must commit before fresh S00-003 continuation; parent
+installation and browser/WSS/interoperability acceptance remain separate work.
+Temporary paths may expire; repeat the scoped probe if needed.