Plan Review Ceo — Scope challenge + 11-section review

Adversarial CEO-style review of the implementation plan. Inputs - pitch (required unless the user explicitly opts into refactor mode, in which case the skill proceeds pitch-less) AND design handoff note at `.claude/immutable/design/{slug}.md` written by `/immutable:design` (expected, warn-on-absence — NOT hard-refused; absence triggers an explicit AskUserQuestion 3-way pause+run-design / proceed-degraded / abort so the user owns the choice consciously rather than the skill silent-skipping app-side context). Pre-existing linked ADRs are referenced if present but are NOT a prerequisite — ADR-authoring triggers are surfaced as an OUTPUT of this review (Phase 3.2), not consum…