[Spike-1040] Add codegen invalidation findings

sequenceDiagram
  autonumber
  participant investigation as Investigation
  participant recommendation as Recommendation
  participant validation as CI Validation
  participant handoff as Handoff
  investigation->>investigation: Findings pass 1
  investigation->>investigation: Pass 3 + reconciliation
  investigation->>recommendation: RSC-first hybrid
  recommendation->>validation: Note lands
  validation->>validation: codegen · lint · typecheck · test · build
  validation->>handoff: All green
  handoff->>handoff: 1 ADR + 2 Stories queued