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>

shell/effects/runner.go

@@ -23,6 +23,7 @@ type Result struct {
 type MatrixSender interface {
 	SendText(ctx context.Context, roomID, text string) error
 	SendMarkdown(ctx context.Context, roomID, markdown string) error
+	SendReplyMarkdown(ctx context.Context, roomID, inReplyTo, markdown string) error
 	SendTyping(ctx context.Context, roomID string, typing bool) error
 }
 
@@ -66,7 +67,12 @@ func (r *Runner) executeOne(ctx context.Context, roomID string, a decision.Actio
 		if a.Reply.ThreadID != "" {
 			target = a.Reply.ThreadID
 		}
-		err := r.matrix.SendMarkdown(ctx, target, a.Reply.Content)
+		var err error
+		if a.Reply.InReplyTo != "" {
+			err = r.matrix.SendReplyMarkdown(ctx, target, a.Reply.InReplyTo, a.Reply.Content)
+		} else {
+			err = r.matrix.SendMarkdown(ctx, target, a.Reply.Content)
+		}
 		return Result{Action: a, Output: a.Reply.Content, Err: err}
 
 	case decision.ActionKindSSH:

shell/matrix/client.go

@@ -305,6 +305,21 @@ func mdToHTML(md string) string {
 	return buf.String()
 }
 
+// SendReplyMarkdown sends a formatted message as a reply to a specific event.
+// It sets m.in_reply_to so Matrix clients show the original message as a quote.
+func (c *Client) SendReplyMarkdown(ctx context.Context, roomID, inReplyTo, markdown string) error {
+	html := mdToHTML(markdown)
+	content := event.MessageEventContent{
+		MsgType:       event.MsgText,
+		Body:          markdown,
+		Format:        event.FormatHTML,
+		FormattedBody: html,
+		RelatesTo:     (&event.RelatesTo{}).SetReplyTo(id.EventID(inReplyTo)),
+	}
+	_, err := c.raw.SendMessageEvent(ctx, id.RoomID(roomID), event.EventMessage, content)
+	return err
+}
+
 // SendReaction sends a reaction to an event.
 func (c *Client) SendReaction(ctx context.Context, roomID, eventID, reaction string) error {
 	_, err := c.raw.SendReaction(ctx, id.RoomID(roomID), id.EventID(eventID), reaction)
@@ -448,6 +463,11 @@ func truncateKey(key string) string {
 	return key
 }
 
+// SetPresence sets the bot's presence status (online, unavailable, offline).
+func (c *Client) SetPresence(ctx context.Context, status event.Presence) error {
+	return c.raw.SetPresence(ctx, status)
+}
+
 // Raw returns the underlying mautrix.Client for advanced use.
 func (c *Client) Raw() *mautrix.Client {
 	return c.raw

shell/matrix/listener.go

@@ -134,6 +134,7 @@ func (l *Listener) Run(ctx context.Context) error {
 			isDM,
 			opts,
 		)
+		msgCtx.EventID = evt.ID.String()
 
 		l.logger.Debug("message parsed",
 			"sender", msgCtx.SenderID,