docs(issue-5): phase 1 benchmark results, contract mapping, task checklist

Records the measured numbers and syncs every document that names the
delegation script paths, then bumps the framework to 4.3.0 in the three-way
lockstep (lib.sh, VERSIONS.md current + matrix, eight SKILL.md frontmatters).

phase1-benchmark.md carries both arms. The deterministic fake transport is what
CI asserts on: 50 publishes cost 50 connections one-shot and 1 persistent, p50
54.813ms -> 0.002ms. The real broker run is informational, since the PoC
default is a public broker: p50 1892.728ms -> 275.992ms, about 85% off.

It also corrects the plan's own estimate rather than repeating it. D8 predicted
the new shell path would drop from 3 forks to 2; the implementation is still 3,
because keeping the `_delegate_script publish_event.py` lookup is the only
thing that produces the "missing script tree does nothing" non-fatal contract
that C-02 pins. Saving that fork would change the contract, so it is deferred
to phase 4 rather than taken quietly.

SKILL.md gains the context table saying which tree wins where, so an operator
reading it knows a frozen loop runs frozen delegation code. The script paths in
every document remain correct and every quoted command still works verbatim.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UrDNJkHmm18uu7n7JwV5Qd

.agents/skills/multi-agent-mux-delegate-job/README.md

@@ -7,5 +7,6 @@
 - 브로커 PoC→운영 전환: [`mqtt-broker-setup.md`](./mqtt-broker-setup.md)
 - 레지스트리 포맷/동시성: [`registry.md`](./registry.md)
 - 참조 구현: [`multi-agent-mux-delegate-job`](./multi-agent-mux-delegate-job) (bash wrapper), [`scripts/publish_event.py`](./scripts/publish_event.py), [`scripts/job_subscriber.py`](./scripts/job_subscriber.py), [`scripts/registry.py`](./scripts/registry.py), [`scripts/mqtt_common.py`](./scripts/mqtt_common.py)
+- **v4.3.0 이후**: 위 `scripts/*.py`는 호환 shim이며 실제 구현은 `.agents/skills/lib_py/delegation/`에 있다 (issue #5 phase 1). 스크립트 경로와 CLI 계약은 그대로이며, `lib.sh` 헬퍼는 `python -m lib_py.delegation.cli`를 호출한다.
 - 영구 감사 로그: `.mam/delegate_job_logs/<job_id>/` (`meta.json`·`events.ndjson`·`status.json`)
   — `multi-agent-mux-delegate-job logs <id>` 또는 `multi-agent-mux-delegate-job logs --list`로 조회 (SKILL.md "Audit Logs" 참조)