fix(config): reject reflector entries without protocols

src/settings/validation.rs

@@ -212,6 +212,15 @@ impl ReflectorSettings {
             );
         }
 
+        for (index, reflector) in self.entries.iter().enumerate() {
+            if reflector.protocols.is_empty() {
+                report.error(
+                    "reflectors.entries",
+                    format!("entry {index} must have at least one measurement protocol"),
+                );
+            }
+        }
+
         for (index, file) in self.files.iter().enumerate() {
             if file.trim().is_empty() {
                 report.error(