feat: add plgreload tool for atomic plugin reload

- Agent can now call plgreload to reload plugins/ directory
- Atomic swap: new devices Start → routes swapped → old devices Stop
- Output channel capability validation on output_send
- output_list_channels tool for channel discovery
- OneBot V11 protocol implementation (Reverse WebSocket)
- Plugin = container with embedded IO channel (composition)
- Unified ToolDef type (agentIO.ToolDef = plugin.ToolDef)

cmd/homed/main.go

@@ -251,6 +251,8 @@ func main() {
 		DocStore:     docStore,
 		Knowledge:    ks,
 		Personality:  personality,
+		PluginReg:    pluginReg,
+		PluginDir:    filepath.Join(cfg.Daemon.DataDir, "plugins"),
 	})
 	agent.Start()
 	defer agent.Stop()
@@ -292,12 +294,4 @@ func main() {
 	log.Printf("[homed] stopped")
 }
 
-func countIOPlugins(r *plugin.Registry) int {
-	n := 0
-	for _, p := range r.List() {
-		if p.IOConfig() != nil {
-			n++
-		}
-	}
-	return n
-}
+