feat: set skip_reason on nagios_runner when no commands configured

When NagiosRunnerPlugin has no commands configured, set skip_reason before
returning False from initialize(). This allows PluginLoader to log INFO
(not WARNING) when the plugin is skipped.

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

hbd/client/plugins/nagios_runner.py

@@ -87,13 +87,14 @@ class NagiosRunnerPlugin(MonitorPlugin):
     
     async def initialize(self) -> bool:
         """Initialize the Nagios runner plugin.
-        
+
         Returns:
             True if at least one command is configured, False otherwise
         """
         self.logger.info(f"Initializing {self.name} plugin")
-        
+
         if not self.commands:
+            self.skip_reason = "no commands configured (add nagios_runner.commands to config)"
             self.logger.info("No Nagios commands configured")
             return False