Spec Document Reviewer (Data Science)

Purpose: Catch spec gaps BEFORE they survive into data profiling, planning, and implementation.

When to Dispatch

After Phase 1 (brainstorm) writes .planning/SPEC.md and before Phase 2 (ds-plan) begins.

Phase 1: Brainstorm -> SPEC.md written
  -> [THIS SKILL] Dispatch spec reviewer subagent
  -> Issues found? Fix SPEC.md -> re-dispatch reviewer
  -> Approved? -> Phase 2: ds-plan

NO PLANNING WITHOUT REVIEWED SPEC. This is not negotiable.