feat: respuestas como reply de Matrix + presencia online/offline

Añade soporte para que las respuestas de los bots sean replies nativos
de Matrix (m.in_reply_to) en lugar de mensajes sueltos. Los clientes
Matrix mostrarán el mensaje original citado.

Cambios:
- EventID en MessageContext para capturar el ID del evento entrante
- InReplyTo en ReplyAction para indicar a qué evento responder
- SendReplyMarkdown en el cliente Matrix (shell/matrix/client.go)
- Runner usa SendReplyMarkdown cuando InReplyTo está presente
- runtime.go pasa InReplyTo en todas las respuestas LLM y comandos
- SetPresence online al arrancar, offline al apagar (graceful)

No se tocan: herramientas, TUI, configuración de agentes.

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

agents/runtime.go

@@ -285,6 +285,18 @@ func (a *Agent) Run(ctx context.Context) error {
 		"tools", a.toolReg.Names(),
 	)
 
+	// Set presence to online
+	if err := a.matrix.SetPresence(ctx, event.PresenceOnline); err != nil {
+		a.logger.Warn("failed to set presence online", "err", err)
+	}
+	defer func() {
+		// Use background context since ctx is already cancelled at shutdown
+		offlineCtx := context.Background()
+		if err := a.matrix.SetPresence(offlineCtx, event.PresenceOffline); err != nil {
+			a.logger.Warn("failed to set presence offline", "err", err)
+		}
+	}()
+
 	// Start bus listener if connected to the orchestration bus
 	if a.agentBus != nil {
 		ch := a.agentBus.Subscribe(bus.AgentID(a.cfg.Agent.ID))
@@ -453,14 +465,14 @@ func (a *Agent) handleEvent(ctx context.Context, msgCtx decision.MessageContext,
 		if handler, ok := a.commands[cmdName]; ok {
 			a.logger.Info("command_executed", "command", cmdName)
 			reply := handler(ctx, msgCtx)
-			_ = a.matrix.SendMarkdown(ctx, roomID, reply)
+			_ = a.matrix.SendReplyMarkdown(ctx, roomID, msgCtx.EventID, reply)
 			return
 		}
 
 		// Unknown command — never falls through to rules or LLM
 		a.logger.Info("command_unknown", "command", msgCtx.Command)
-		_ = a.matrix.SendMarkdown(ctx, roomID,
-			fmt.Sprintf("Comando desconocido: !%s. Usa !help para ver comandos disponibles.", msgCtx.Command))
+		_ = a.matrix.SendReplyMarkdown(ctx, roomID, msgCtx.EventID,
+			fmt.Sprintf("Comando desconocido: `!%s`. Usa `!help` para ver comandos disponibles.", msgCtx.Command))
 		return
 	}
 
@@ -502,7 +514,7 @@ func (a *Agent) executeActions(ctx context.Context, roomID string, msgCtx decisi
 				a.logger.Warn("LLM action requested but no LLM configured")
 				expanded = append(expanded, decision.Action{
 					Kind:  decision.ActionKindReply,
-					Reply: &decision.ReplyAction{Content: "Este bot no tiene LLM configurado."},
+					Reply: &decision.ReplyAction{Content: "Este bot no tiene LLM configurado.", InReplyTo: msgCtx.EventID},
 				})
 				continue
 			}
@@ -518,12 +530,12 @@ func (a *Agent) executeActions(ctx context.Context, roomID string, msgCtx decisi
 				a.logger.Error("llm error", "err", err)
 				expanded = append(expanded, decision.Action{
 					Kind:  decision.ActionKindReply,
-					Reply: &decision.ReplyAction{Content: "Sorry, I encountered an error."},
+					Reply: &decision.ReplyAction{Content: "Sorry, I encountered an error.", InReplyTo: msgCtx.EventID},
 				})
 			} else {
 				expanded = append(expanded, decision.Action{
 					Kind:  decision.ActionKindReply,
-					Reply: &decision.ReplyAction{Content: reply},
+					Reply: &decision.ReplyAction{Content: reply, InReplyTo: msgCtx.EventID},
 				})
 
 				// Memory: append assistant reply after LLM call