feat: implementar comandos custom !echo y !dice para test-bot

- !echo <texto>: repite el texto recibido (util para assertions exactas)
- !dice / !dado: lanza un dado aleatorio (1-6)
- Registro en cmd/launcher/main.go via testbot.Commands()

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cmd/launcher/main.go

@@ -33,7 +33,7 @@ import (
 	_ "github.com/enmanuel/agents/agents/assistant-bot"
 	_ "github.com/enmanuel/agents/agents/asistente-2"
 	_ "github.com/enmanuel/agents/agents/meteorologo"
-	_ "github.com/enmanuel/agents/agents/test-bot"
+	testbot "github.com/enmanuel/agents/agents/test-bot"
 )
 
 func main() {
@@ -181,6 +181,13 @@ func main() {
 						agentCleanup()
 						continue
 					}
+					// Register agent-specific commands for robots
+					if cfg.Agent.ID == "test-bot" {
+						for _, cmd := range testbot.Commands() {
+							robot.RegisterCommand(cmd.Spec, cmd.Handler)
+						}
+					}
+
 					runner = robot
 					agentLogger.Info("created robot", "id", cfg.Agent.ID)
 				} else {