(new): webhook + payload error sentinels

(fix): polling panic ErrorEvent, nil-logger guard
  (refactor): inline webhook errors → sentinels, dead Runner branch
  (doc): Runner godoc, Error godoc, drafts cleanup

plugins.go

@@ -106,9 +106,8 @@ func (p *Plugin[T]) AddScene(scene *Scene[T]) *Plugin[T] {
 		return p
 	}
 	scene.pluginName = p.name
-	scene.setPluginName(p.name)
 	if _, exists := p.scenes[scene.name]; exists && p.logger != nil {
-		p.logger.Warnf("scene '%s' is already registered in plugin '%s'; overwriting", scene.name, p.name)
+		p.logger.Warnf("scene '%s' already registered in plugin '%s'; overwriting", scene.name, p.name)
 	}
 	p.scenes[scene.name] = scene
 	return p