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

templates/project-profile.yml

@@ -75,6 +75,9 @@ pipeline:
   debug:      { trigger: bug, red_first: true }
   # tdd:       { trigger: test_specifiable_feature, red_first: true, alt_to: brainstorm }  # opt-in: executable-spec-first entry, alternative to brainstorm
   # boss:      { user_invoked: true }     # autonomous orchestrator mode, /boss
+  #   spec_auto_sign: false               # opt-in: let /boss sign a spec in the user's place when all
+  #                                       # objective gates are green AND a unanimous spec-skeptic panel
+  #                                       # passes; default off (human signature mandatory). See profile-schema.md.
   # fieldtest:           { boss_only: true, when: surface_touch }   # per-cycle usability test
   # milestone_fieldtest: { boss_only: true, when: surface_touch, gates_close: milestone }  # closing gate: end-to-end proof of the milestone's promise
   # docwriter: { boss_only: true, when: api_stable_across_n_cycles }