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-monitor/SKILL.md

@@ -1,7 +1,7 @@
 ---
 name: multi-agent-mux-monitor
 description: "Run a long-lived reconciler that watches .mam/agent-sessions.yaml against the actual herdr/agent runtime state and reconciles them. Use when you want live visibility into which agent sessions are running, which are dead, which have stale YAML entries, and which have new session ids that haven't been recorded yet. Runs as a persistent loop (`reconcile.sh --subscribe`) that keeps going until it times out, idles out, or is interrupted."
-version: 4.2.0
+version: 4.3.0
 author: godopu
 license: MIT
 platforms: [linux, macos]