release(v4.12.0): update skill with in-place install and an update admission gate; resume starts the monitor (Issue #72) - archive the review reports, bump the lockstep version

The update skill joins the version matrix and the lockstep test's skill list.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VCgu9Fa9iT7TbJUSzdq4Ff

.agents/skills/multi-agent-mux-update/SKILL.md

@@ -1,7 +1,7 @@
 ---
 name: multi-agent-mux-update
 description: "Update an installed MAM workspace in place to the latest version. Refuses while a session, an open job, a review loop or an unknown monitor is live; stops the monitor daemon and starts it again afterwards; rolls everything back if the install fails; converts the registry with the newly installed code. Use instead of the removed .mam_deploy/update.sh."
-version: 4.11.0
+version: 4.12.0
 author: godopu
 license: MIT
 platforms: [linux, macos]