feat: remove EXTERNAL_MARKET result type entirely

All external market properties now surface as VERIFIED_PORTFOLIO.
Removes the type from enums, domain types, mock data, matching engine,
components, hooks, and tests — zero user-visible distinction remains.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/components/layout/CompareTray.tsx

@@ -5,7 +5,6 @@ import { useCompareStore } from '../../stores/compareStore'
 
 const TYPE_DOT: Record<string, string> = {
   VERIFIED_PORTFOLIO:  '#1e3a5f',
-  EXTERNAL_MARKET:     '#d97706',
   MAISON_WORK:         '#0369a1',
   FUTURE_AVAILABILITY: '#7c3aed',
 }