fix(cortex): integrate intake intents into full chat + artifact flow

Fixes 4 bugs preventing intake blocks from working:

1. Chat API validation: Add 'nudge' to message type enum, allow empty
   content for streaming messages
2. AI chat recognition: Add P3 intake intents (intake_status,
   risico_query, diagnose_query, intake_navigeer) to system prompt
   with triggers, entities, and JSON examples
3. Artifact rendering: Add intake block imports and switch cases
   to artifact-container.tsx
4. API 400 error: Convert null to undefined for optional Zod params
   (searchParams.get returns null, Zod .optional() expects undefined)

Also adds:
- Testplan for E2E testing (60+ test cases)
- Session log with lessons learned and new intent checklist

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/api/cortex/intake/diagnose/route.ts

@@ -74,7 +74,7 @@ export async function GET(request: NextRequest) {
     // Parse and validate query parameters
     const searchParams = request.nextUrl.searchParams;
     const patientId = searchParams.get('patientId');
-    const intakeId = searchParams.get('intakeId');
+    const intakeId = searchParams.get('intakeId') || undefined; // Convert null to undefined for Zod
 
     if (!patientId) {
       return NextResponse.json(