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/job-protocol.md

@@ -112,3 +112,7 @@ On `broker.hivemq.com` anyone can publish/subscribe the same topic. Therefore:
   subscriber **before** the agent (ordering dependency), or rely on retained
   terminal events in production.
 - Real operational decisions belong to the own-broker stage with auth + ACL.
+
+---
+
+> **구현 위치 각주 (v4.3.0)**: 본 문서가 인용하는 `scripts/*.py` 경로는 유효하며 계약도 불변이다. 실제 구현은 issue #5 phase 1에서 `.agents/skills/lib_py/delegation/`으로 이동했고, `scripts/*.py`는 그 패키지를 자기 옆 트리에 바인딩하는 호환 shim이다.