release(v4.8.6): Issue #17 item 4 - archive PR #51 reviews and bump the lockstep version

Merge-workspace review: round 1 (@518beda) claude agy grok PASS, codex
NOT PASS (finalize wait measured on the wall clock); fixed in 4c86107.
Round 2 delta (@4c86107) claude agy grok PASS; codex (24b21b9c, after
817d1650 closed deadline_timeout with no report) found R1 closed and no
new defect, but withheld PASS only because its sandbox could not bind
the suite's loopback broker. The same two-file suite run here at
4c86107: 278 passed. Full suite at 518beda on macOS / Python 3.9:
1711 passed / 1 failed / 38 skipped; the failure
(test_issue45_restore, herdr 0.9.3 cwd restore) also fails on main.

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

.agents/skills/lib.sh

@@ -29,7 +29,7 @@ export WORKSPACE_ROOT
 # Framework semantic version. Single runtime source of truth; kept in lockstep
 # with VERSIONS.md and the 8 SKILL.md frontmatters by tests/test_version_consistency.py.
 # NOTE: unlike other MAM_* variables this one is intentionally NOT env-overridable.
-MAM_VERSION="4.8.5"
+MAM_VERSION="4.8.6"
 export MAM_VERSION
 AGENT_SESSIONS_YAML="${AGENT_SESSIONS_YAML:-$WORKSPACE_ROOT/.mam/agent-sessions.yaml}"