feat(agent-skill): give the codeman skill to every agent CLI, not just Claude

The agent skill only reached Claude Code: injection wrote
.claude/skills/codeman, which no other CLI reads, and the per-session
preamble was seeded for claude alone. A Codex, Gemini, OpenCode,
Antigravity, Grok, DeepSeek or OMP session inside Codeman never learned it
could start and drive workers.

- Registry field capabilities.agentSkillDir (a closed enum, since
  clis.json can set it and it decides where the server writes) names the
  skills directory each CLI scans. Claude keeps .claude/skills; those seven
  CLIs get the same skill in <case>/.agents/skills/codeman (each measured to
  scan it; Claude Code does not, so it never sees two copies). pi gets none:
  a project skill makes pi ask "Trust project folder?" at startup.
- The preamble is seeded for every local session whose CLI takes the
  skill; nothing in it is claude-specific.
- The skill text is CLI-neutral and names the two CLI-side failures to
  report instead of retrying: a sandbox that blocks loopback (Codex's
  default), and commands that do not carry this session's environment
  (Codex 0.162 runs them in a shared app-server daemon).
- POST /api/sessions injects after the launch pre-flight, so a CLI that
  cannot start leaves nothing in the workspace.
- codeman skill install gains --mode; uninstall --case removes the copy
  from every directory the registry can write.
- The settings toggle moves to Agents & CLIs > All agent CLIs.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/wiki/Settings-Reference.md

@@ -145,7 +145,7 @@ instead of its native cloud backend. See [Custom Model Endpoints](Custom-Model-E
 | Allowed Tools                    | The list used by the explicit mode.                                                            |
 | Ralph / Todo Tracker             | Enables the Ralph loop surfaces.                                                               |
 | Agent Teams                      | Experimental teams. Also needs the CLI's own environment flag.                                 |
-| Codeman Agent Skill              | Injects the agent skill into new Claude sessions per case. Off by default. See [Driving Codeman From An Agent](Driving-Codeman-From-An-Agent). |
+| Codeman Agent Skill              | Under **All agent CLIs**. Injects the agent skill into each new session's case, where that session's CLI looks for skills (every CLI except Pi and a plain shell). Off by default. See [Driving Codeman From An Agent](Driving-Codeman-From-An-Agent). |
 | Remote auto-reconnect            | Reattaches dropped remote SSH sessions. On by default.                                         |
 | Nice priority / value            | Runs agent processes at a lower CPU priority.                                                  |
 | Default Codex model              | Model for new local Codex sessions; empty uses Codex's own config. Letters, digits, `.` `_` `-` `/` only. |