chore(release): bump framework and 8 skills to v4.0.0 (MAJOR — cline removal & hermes modernization)

- Bump MAM_VERSION to 4.0.0 in lib.sh
- Bump all 8 skill frontmatter versions to 4.0.0 in 3-way lockstep
- Update VERSIONS.md with v4.0.0 changelog, migration guide (B-1..B-5), and skill matrix
- Archive multi-agent version upgrade consensus and peer review reports (439 passed, 0 failures)

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

@@ -1,7 +1,7 @@
 ---
 name: multi-agent-mux-stop
 description: "Stop an agent herdr session (claude, antigravity/agy) and update .mam/agent-sessions.yaml. Default stops gracefully and marks status=stopped with conversation preserved for resume. Does NOT delete on-disk conversation artifacts (jsonl/db) — those are preserved unless --purge-conversation is passed. Use when ending a work session, switching to a different one, or cleaning up before a fresh start."
-version: 3.1.0
+version: 4.0.0
 author: godopu
 license: MIT
 platforms: [linux, macos]