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-create/SKILL.md

@@ -1,7 +1,7 @@
 ---
 name: multi-agent-mux-create
 description: "Create a new agent session (claude, antigravity/agy) in a dedicated herdr session for context-preserving long-running work. Always creates a herdr session — never backgrounds with nohup/disown. Writes the new session to .mam/agent-sessions.yaml. Use when you want to start a fresh agent (no prior UUID) for a new project workspace."
-version: 4.2.0
+version: 4.3.0
 author: godopu
 license: MIT
 platforms: [linux, macos]