fix: React error #31 - Cannot render signal objects directly

Root Cause:
- WorkflowResultViewer tried to render NormalizedSignal objects directly
- React Error #31: "Objects are not valid as a React child"
- Caused white screen crash after workflow execution

Frontend WorkflowResultViewer.jsx:
- Fixed signal rendering in "All Signals" section
- Now displays: question_type: normalized_value (status)
- Proper formatting for signal objects

Before:
  • {signal}  ❌ renders [object Object]

After:
  • protein_intake: optimal (valid) ✅

Impact:
- Workflow execution no longer crashes the UI
- Signals are properly displayed
- Users can see normalized decision signals

Issue: White screen after workflow execution
Version: 0.9p (workflow module)
Part 3: End Node Template Engine - UI Fix

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

frontend/src/components/workflow/panels/WorkflowResultViewer.jsx

@@ -171,8 +171,14 @@ export function WorkflowResultViewer({ result, onClose }) {
               }}
             >
               {aggregated.all_signals.map((signal, idx) => (
-                <div key={idx} style={{ marginBottom: '8px' }}>
-                  • {signal}
+                <div key={idx} style={{ marginBottom: '8px', fontFamily: 'monospace' }}>
+                  <div>
+                    <strong>{signal.question_type || 'unknown'}:</strong>{' '}
+                    {signal.normalized_value || signal.raw_value || 'null'}{' '}
+                    <span style={{ color: 'var(--text3)' }}>
+                      ({signal.status})
+                    </span>
+                  </div>
                 </div>
               ))}
             </div>