feat(boss): opt-in spec auto-sign via adversarial spec-skeptic panel

Add `pipeline.boss.spec_auto_sign` (default off). With it on, a /boss
run may sign a spec in the user's place — but only through a gate built
to never rely on the orchestrator's own confidence: all objective gates
green (precondition, parse, grounding-check PASS with no human override)
AND a unanimous five-lens adversarial spec-skeptic panel (criterion,
grounding, scope-fork, ambiguity, plan-readiness). Any single BLOCK
falls back to the human sign-off pause.

On a clean sign the orchestrator commits the spec ((boss-signed) in the
subject), fires a mandatory informational-with-veto notify, and proceeds
to planner without stopping. A later veto is a forward correction, never
a history rewind.

- new agent: specify/agents/spec-skeptic.md (read-only, one lens per dispatch)
- specify Step 6 + Iron Law: approval may come from the auto-sign gate,
  never from model self-confidence
- boss: third notify category, §"Spec auto-sign", rationalisations, red flags
- profile-schema + template: the opt-in slot
- pipeline.md, agent-template.md, README: the auto-sign path documented

docs/pipeline.md

@@ -104,6 +104,14 @@ interview. Bounces to `brainstorm` the moment the sources do not
 resolve a load-bearing design decision. A core node, not opt-in
 (unlike `tdd`).
 
+The sign-off is the user's by default, including under `/boss`. The
+one exception is the opt-in `pipeline.boss.spec_auto_sign` slot: with
+it on, a `/boss` run may sign a spec in the user's place — but only
+when every objective gate is green AND a unanimous five-lens
+`spec-skeptic` panel passes; the orchestrator's own confidence never
+signs. Any juror `BLOCK` falls back to the human sign-off pause. See
+`../specify/SKILL.md` Step 6 and `../boss/SKILL.md` §"Spec auto-sign".
+
 ### planner
 
 Hard-gate before implement. Produces a placeholder-free,