Claude Code: Fix Cain A2A status display - add explicit health and error_display fields

- Add health field (HEALTHY/ERROR) to avoid parsing ambiguity
- Add error_display field to prevent "unknown" string confusion
- Push A2A diagnostic improvements

app.py

@@ -455,7 +455,8 @@ try:
         "stage": "RUNNING_A2A_READY",
         "last_updated": datetime.utcnow().isoformat() + "+00:00",
         "agent": "cain",
-        "error": None,
+        "error": None,  # ALWAYS null for healthy state
+        "error_display": "None",  # Explicit display field to avoid "unknown" parsing issues
         "startup_checks": {
             "openclaw_imported": False,
             "brain_imported": False
@@ -475,17 +476,23 @@ try:
         status_data["startup_checks"]["brain_imported"] = True
         # CRITICAL: Explicitly set error to null when imports succeed
         status_data["error"] = None
+        status_data["error_display"] = "None"
+        status_data["health"] = "HEALTHY"
     except Exception as e:
         error_msg = f"{type(e).__name__}: {e}"
         # CRITICAL: Never write "unknown" as error - use specific error or None
         # "unknown" is treated as null/healthy, so avoid ambiguity
         if error_msg.strip().lower() in ("unknown", "none", "null", ""):
             status_data["error"] = None
+            status_data["error_display"] = "None"
+            status_data["health"] = "HEALTHY"
         else:
             status_data["error"] = error_msg
+            status_data["error_display"] = error_msg
+            status_data["health"] = "ERROR"
 
     # Add explanatory note about error field semantics
-    status_data["_note"] = "error=null means healthy - null or 'unknown' string are both treated as 'no error'"
+    status_data["_note"] = "error=null means healthy - health field is authoritative"
 
     # Write to ALL possible locations to ensure consistency and prevent stale errors
     all_status_paths = [