feat(skill): add the agent-skill install layer and harden the packaged skill

Ship `skills/codeman` as an installable Claude Code skill rather than a
repo-only reference, and fix six defects found while verifying it live.

Install layer:
- `codeman skill install [--case <name>]` / `codeman skill uninstall`.
  Case names resolve through linked-cases.json first, mirroring the
  server's resolveCasePath(), so a case linked in from outside
  ~/codeman-cases no longer fails with "Case not found".
- applyAgentSkill() / installAgentSkillInto() / removeAgentSkillFrom() in
  hooks-config.ts. Copies are marker-owned, so an unmarked user-authored
  skill is never touched, and a symlinked skill dir is refused (this
  repo's own .claude/skills/codeman is a symlink to the source).
- Synced `agentSkillEnabled` setting, default OFF: schemas.ts,
  ports/config-port.ts, server.ts, session-routes.ts (add-only injection
  on Claude session create and quick-start), plus the App Settings toggle.

Skill content fixes, each reproduced before and after:
- Fail-closed `delete_session` replaces `is_self ... || curl -X DELETE`.
  Shell state does not survive between agent tool calls, and an undefined
  is_self exited 127, firing the `||` branch and deleting the caller's own
  session with the one guard bypassed. The request now lives inside the
  guard, so a lost preamble deletes nothing.
- clientId is a fixed literal instead of `agent-$$`. The pid changes per
  tool call, so the documented resend-identical-request loop stopped being
  a duplicate and retyped the prompt, submitting the turn twice.
- `last-response` is now the documented read path for claude and codex
  workers. It returns clean transcript text; the terminal scrape it
  replaces returns a wall of TUI repaint noise. Its transcript flush lags
  the stop signal, so the recipes poll it rather than reading once.
- quick-start examples branch on `.success`. Previously a failed spawn
  yielded the literal session id "null" and burned the whole readiness
  budget before reporting jq noise instead of the cause.
- Documented that turning `agentSkillEnabled` off sweeps nothing, and
  corrected the hooks-config comment that claimed a toggle-off sweep
  exists. Per-case cleanup is `codeman skill uninstall --case <name>`.
- Documented that SESSION_BUSY means the 50-session cap on quick-start,
  and that caseName resolves linked cases, so a generic name can land a
  worker in a real repo.

Tests: test/agent-skill.test.ts covers install, refresh, idempotence,
marker ownership and symlink refusal against the real packaged source;
test/quick-start.test.ts covers injection behind the setting.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

README.md

@@ -691,6 +691,18 @@ Single-digit selection (1-9), color-coded status, token counts, auto-refresh. De
 
 For AI agents and automation that control Codeman without a browser: an agent that spins up worker sessions, a CI bot, or **Claude Code running _inside_ a Codeman session orchestrating other sessions**. Everything the UI does is HTTP + a CLI, so an agent can do it too.
 
+> **Shortcut: install the packaged agent skill.** Everything below (plus worked multi-worker recipes) ships as a Claude Code skill in [`skills/codeman`](skills/codeman/SKILL.md), so an agent inside a session can drive Codeman without you pasting docs into the prompt. Three ways to get it:
+>
+> - `npx skills add Ark0N/Codeman --skill codeman -g`: global, works for any skills-aware agent
+> - `codeman skill install` (global) or `codeman skill install --case <name>`: for npm installs that never cloned the repo; `codeman skill uninstall` reverses it
+> - **App Settings → Agent Skill** (`agentSkillEnabled`, default off): Codeman then injects the skill into each case on Claude session create; a user-authored `skills/codeman` in the case is never overwritten
+>
+> A global install (`codeman skill install`, or `npx skills add`) is picked up by **every new Claude Code session on the machine**, inside Codeman or not. The skill self-gates: outside a Codeman session (`CODEMAN_MUX` unset) it refuses to act, so a global install costs an idle session nothing.
+>
+> ⚠️ Turning `agentSkillEnabled` back off **does not remove already-injected copies** (a create-time sweep would yank the skill out from under other live sessions sharing that `.claude/` dir). Remove them per case with `codeman skill uninstall --case <name>`.
+
+
+
 ### Detect that you're inside Codeman
 
 When a CLI runs in a Codeman-managed session, these environment variables are set — read them instead of hardcoding anything: