docs: add project classification and vision discovery to PRD

bmad/_bmad-output/planning-artifacts/prd.md

@@ -1,8 +1,13 @@
 ---
-stepsCompleted: ['step-01-init']
+stepsCompleted: ['step-01-init', 'step-02-discovery']
 inputDocuments:
   - '_bmad-output/brainstorming/brainstorming-session-2026-04-12-001.md'
 workflowType: 'prd'
+classification:
+  projectType: 'web_app'
+  domain: 'general'
+  complexity: 'low'
+  projectContext: 'greenfield'
 ---
 
 # Product Requirements Document - try-bmad