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>

CLAUDE.md

@@ -182,7 +182,7 @@ Codeman is a Claude Code session manager with web interface and autonomous Ralph
 
 **Input**: `session.writeViaMux()` for programmatic/curl input via tmux `send-keys -l` + `send-keys Enter`, single-line only. Interactive **browser** input goes through a durable **exactly-once** layer: a stable `clientId` + monotonic per-session `seq` persisted to localStorage until the server ACKs, so a dropped link cannot lose or double-deliver a prompt. `ws-connection-registry.ts` supersedes only same-TAB reconnects, so two tabs on one session coexist. → [architecture-invariants#input-delivery-and-ws-resilience](docs/architecture-invariants.md#input-delivery-and-ws-resilience)
 
-**Agent wait primitives**: bounded long-polls so an agent driving Codeman from a shell can block instead of poll: `GET /api/sessions/:id/wait` (lifecycle signal), `GET /api/sessions/:id/wait-output` (literal substring, **never** regex) and `wait`/`waitTimeout` on `POST /api/sessions/:id/input`. Registry in `session-wait-registry.ts` (pure, no `Session` reference), bounds in `config/agent-wait.ts`. ⚠️ **A timeout is a 200** (`wait.timedOut`), never an error, so callers loop over short waits. ⚠️ `stop`/`blocked` come from Claude Code hooks and therefore fire for **`claude` mode ONLY** (`shell` installs none either); asking for one explicitly on another mode is a 400, the default set silently drops them. ⚠️ Send-and-wait registers the waiter BEFORE the write (a separate POST-then-wait races and reports the PREVIOUS turn), and both teardown paths must `notifySignal('exit')` BEFORE `cancelAll()`. ⚠️ Client-hangup abort listens on **`reply.raw`** guarded by `writableFinished`: on `req.raw`, `close` fires when the request BODY ends, which on a POST killed every send-and-wait instantly and no `app.inject()` test could see it. ⚠️ Worker liveness cannot come from `session.pid` — for a tmux session that is the local attach client, which outlives a worker dying inside its pane — so it is probed at the mux layer (`isPaneDead`, ~750 ms cache) on blocking waits only, never on the input hot path. ⚠️ Signals are edge-triggered with no history: one that fires with no waiter registered is unobservable afterwards, so gather fan-outs with send-and-wait or latched `wait-output` markers, never fire-and-forget-then-sequential-signal-waits. → [architecture-invariants#agent-wait-primitives](docs/architecture-invariants.md#agent-wait-primitives), `docs/api-reference.md`
+**Agent wait primitives**: bounded long-polls so an agent driving Codeman from a shell can block instead of poll: `GET /api/sessions/:id/wait` (lifecycle signal), `GET /api/sessions/:id/wait-output` (literal substring, **never** regex) and `wait`/`waitTimeout` on `POST /api/sessions/:id/input`. Registry in `session-wait-registry.ts` (pure, no `Session` reference), bounds in `config/agent-wait.ts`. ⚠️ **A timeout is a 200** (`wait.timedOut`), never an error, so callers loop over short waits. ⚠️ `stop`/`blocked` come from Claude Code hooks and therefore fire for **`claude` mode ONLY** (`shell` installs none either); asking for one explicitly on another mode is a 400, the default set silently drops them. ⚠️ Send-and-wait registers the waiter BEFORE the write (a separate POST-then-wait races and reports the PREVIOUS turn), and both teardown paths must `notifySignal('exit')` BEFORE `cancelAll()`. ⚠️ Client-hangup abort listens on **`reply.raw`** guarded by `writableFinished`: on `req.raw`, `close` fires when the request BODY ends, which on a POST killed every send-and-wait instantly and no `app.inject()` test could see it. ⚠️ Worker liveness cannot come from `session.pid` — for a tmux session that is the local attach client, which outlives a worker dying inside its pane — so it is probed at the mux layer (`isPaneDead`, ~750 ms cache) on blocking waits only, never on the input hot path. ⚠️ Signals are edge-triggered with no history: one that fires with no waiter registered is unobservable afterwards, so gather fan-outs with send-and-wait or latched `wait-output` markers, never fire-and-forget-then-sequential-signal-waits. The primitives are packaged as the **`skills/codeman` agent skill**: installable via `codeman skill install [--case <name>]` / `skill uninstall`, or auto-injected into a case's `.claude/skills/` on Claude session create behind `agentSkillEnabled` (SYNCED, default OFF). Injection is ADD-ONLY at create, marker-owned (`applyAgentSkill` in `hooks-config.ts` never touches an unmarked user copy) and refuses symlinks (this repo's own `.claude/skills/codeman` is a symlink to the source, which the injector must never write through). → [architecture-invariants#agent-wait-primitives](docs/architecture-invariants.md#agent-wait-primitives), `docs/api-reference.md`
 
 **Idle detection**: Multi-layer (completion message → AI check → output silence → token stability). See `docs/respawn-state-machine.md`.