fix: correctly handle curl non-zero exit codes as errors

apps/monitor/src/runner.rs

@@ -194,13 +194,13 @@ async fn run_curl(
 
     let output = cmd.output().await.map_err(|e| format!("curl exec error: {e}"))?;
 
-    if !output.status.success() && output.stdout.is_empty() {
+    if !output.status.success() {
         let stderr = String::from_utf8_lossy(&output.stderr).to_string();
-        // curl exit 28 = timeout
-        let msg = if output.status.code() == Some(28) {
-            format!("timed out after {:.0}s", timeout_secs)
-        } else {
-            stderr.trim().to_string()
+        let msg = match output.status.code() {
+            Some(28) => format!("timed out after {:.0}s", timeout_secs),
+            Some(6)  => "DNS lookup failed".to_string(),
+            Some(7)  => "connection refused".to_string(),
+            _        => stderr.trim().to_string(),
         };
         return Err(msg);
     }