refactor: restore behavior the branch had changed (codex review)

A codex review of the branch found seven places where earlier refactor commits changed behavior. Each is restored here with a test:

- base_service imported flood_scope relatively; the local-service loader also runs that file as local_services.base_service, where the import cannot resolve. Now absolute.
- Radio-health fields were initialized after commands and services were built, so a plugin constructor reading is_radio_offline raised. They are now set before any plugin.
- Removing the per-command can_execute overrides made 31 commands honor skip_channel_check, which their overrides had dropped. BaseCommand.honors_skip_channel_check (False on exactly those commands) keeps them enforcing their channel list.
- CommandManager.get_plugin_metadata, WxCommand.get_weather_for_zipcode and PluginLoader.validate_plugin were public compatibility entry points; they are back.
- feed_manager stopped exporting DEFAULT_MAX_FEED_RESPONSE_BYTES and DEFAULT_MAX_PARSED_FEED_ITEMS despite the commit saying it re-exported them; it does now.
- wx and gwx logged companion-location lookup failures at WARNING; the shared helper logged at debug. It now takes the level.
- The INFO 'MESSAGE ROUTING' / 'DIRECT MESSAGE' lines for pubkey-correlated DMs were removed with the dead path_info computation; they are logged again by a log-only helper.

modules/plugin_loader.py

@@ -539,3 +539,28 @@ class PluginLoader:
             self.logger.error(f"Error reloading plugin {plugin_name}: {e}")
             return False
 
+    def validate_plugin(self, plugin_instance: BaseCommand) -> list[str]:
+        """Validate a plugin instance and return any issues"""
+        issues = []
+        metadata = plugin_instance.get_metadata()
+
+        # Check required metadata
+        if not metadata.get('name'):
+            issues.append("Plugin missing 'name' metadata")
+
+        if not metadata.get('description'):
+            issues.append("Plugin missing 'description' metadata")
+
+        # Check if execute method is implemented
+        if not hasattr(plugin_instance, 'execute'):
+            issues.append("Plugin missing 'execute' method")
+
+        # Check for keyword conflicts
+        for keyword in metadata.get('keywords', []):
+            if keyword.lower() in self.keyword_mappings:
+                existing_plugin = self.keyword_mappings[keyword.lower()]
+                if existing_plugin != metadata['name']:
+                    issues.append(f"Keyword '{keyword}' conflicts with plugin '{existing_plugin}'")
+
+        return issues
+