Claude Code: improve frontend error handling to show HTTP status codes

- Update fetchDebugHealth() to log response.status and response.statusText
- setDebugStatsError() now displays actual status code instead of "Error"
- Network errors show 'NET', HTTP errors show numeric status

frontend/agent-dashboard.html

@@ -860,12 +860,12 @@
                     const data = await response.json();
                     updateDebugStats(data);
                 } else {
-                    console.error('Failed to fetch debug health:', response.statusText);
-                    setDebugStatsError();
+                    console.error('Failed to fetch debug health:', response.status, response.statusText);
+                    setDebugStatsError(response.status);
                 }
-            } catch (error) {
-                console.error('Error fetching debug health:', error);
-                setDebugStatsError();
+            } catch (err) {
+                console.error('Error fetching debug health:', err);
+                setDebugStatsError('NET');
             }
         }
 
@@ -883,11 +883,11 @@
         }
 
         // Set error state for debug stats
-        function setDebugStatsError() {
+        function setDebugStatsError(statusCode = 'ERR') {
             const uptimeEl = document.getElementById('uptime');
             const memoryEl = document.getElementById('memory');
-            if (uptimeEl) uptimeEl.textContent = 'Error';
-            if (memoryEl) memoryEl.textContent = 'Error';
+            if (uptimeEl) uptimeEl.textContent = statusCode;
+            if (memoryEl) memoryEl.textContent = statusCode;
         }
     </script>
 </body>