docs: plugin users and the skill default, and what a local session keeps

The Codeman Agent Skill setting is now on by default, and the per-case
copy it writes lists twice next to the Claude Code plugin (codeman and
codeman:codeman), the same as a codeman skill install would. The README
and the wiki now say so and tell plugin users to turn the setting off.

The README's local model bullet said the session "sends nothing off the
machine". The server keeps the runtime on loopback with its cloud
features off, but opencode itself is not configured offline (its model
catalogue and update checks are untouched), so the bullet now says what
the code does: the prompts and files go to a model on this Mac.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/wiki/Codeman-Skill.md

@@ -54,7 +54,9 @@ Pick one route. The skill only acts inside a Codeman session, so a global instal
 | Web UI             | **App Settings → Agents & CLIs → All agent CLIs → Codeman Agent Skill**         | Injects it into each case when a session is created, where that session's CLI looks: `.claude/skills/` for Claude Code, `.agents/skills/` for Codex, Gemini CLI, OpenCode, Antigravity, Grok, DeepSeek and OMP. On by default since 1.50.0. |
 
 Use the plugin **or** `codeman skill install`, not both: a Claude Code with both lists the
-skill twice (`codeman` and `codeman:codeman`).
+skill twice (`codeman` and `codeman:codeman`). The per-case copy the Codeman Agent Skill
+setting writes (on by default) does the same beside the plugin, so turn that setting off
+if you use the plugin.
 
 The web UI route skips pi, because a project skill makes pi ask to trust the folder at
 startup. A pi or plain shell session uses the [`codeman agent`