fix: responder en thread cuando el mensaje viene de un thread

Dos problemas corregidos:

1. Detección de threads con E2EE: después de desencriptar un evento,
   evt.Content.Raw puede no contener m.relates_to. Se añade fallback
   usando el contenido tipado (evt.Content.Parsed) que es más robusto
   tras la desencriptación de mautrix.

2. Notificaciones de tools fuera del thread: la notificación "🔨 tool"
   se enviaba con SendMarkdown directo a la sala, ignorando el contexto
   de thread. Ahora usa sendReply que respeta ThreadID.

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

shell/matrix/thread_test.go

@@ -2,6 +2,9 @@ package matrix
 
 import (
 	"testing"
+
+	"maunium.net/go/mautrix/event"
+	"maunium.net/go/mautrix/id"
 )
 
 // extractThreadID is the pure logic extracted from the listener for testability.
@@ -93,3 +96,78 @@ func TestExtractThreadID_ThreadWithoutEventID(t *testing.T) {
 		t.Errorf("expected empty string for thread without event_id, got %q", got)
 	}
 }
+
+// extractThreadIDFromParsed is the typed-content fallback for E2EE events.
+// Mirrors the fallback logic in listener.go.
+func extractThreadIDFromParsed(parsed interface{}) string {
+	if msgContent, ok := parsed.(*event.MessageEventContent); ok && msgContent.RelatesTo != nil {
+		if threadParent := msgContent.RelatesTo.GetThreadParent(); threadParent != "" {
+			return string(threadParent)
+		}
+	}
+	return ""
+}
+
+func TestExtractThreadID_TypedFallback_Thread(t *testing.T) {
+	parsed := &event.MessageEventContent{
+		MsgType: event.MsgText,
+		Body:    "hello from thread",
+		RelatesTo: (&event.RelatesTo{}).SetThread(id.EventID("$root123"), id.EventID("$last456")),
+	}
+
+	got := extractThreadIDFromParsed(parsed)
+	if got != "$root123" {
+		t.Errorf("expected $root123 from typed fallback, got %q", got)
+	}
+}
+
+func TestExtractThreadID_TypedFallback_NoRelatesTo(t *testing.T) {
+	parsed := &event.MessageEventContent{
+		MsgType: event.MsgText,
+		Body:    "plain message",
+	}
+
+	got := extractThreadIDFromParsed(parsed)
+	if got != "" {
+		t.Errorf("expected empty string from typed fallback, got %q", got)
+	}
+}
+
+func TestExtractThreadID_TypedFallback_ReplaceNotThread(t *testing.T) {
+	parsed := &event.MessageEventContent{
+		MsgType:   event.MsgText,
+		Body:      "edited",
+		RelatesTo: (&event.RelatesTo{}).SetReplace(id.EventID("$original")),
+	}
+
+	got := extractThreadIDFromParsed(parsed)
+	if got != "" {
+		t.Errorf("expected empty string for m.replace via typed fallback, got %q", got)
+	}
+}
+
+func TestExtractThreadID_RawEmptyTypedWorks(t *testing.T) {
+	// Simulates E2EE scenario: Raw map has no m.relates_to but Parsed does
+	raw := map[string]any{
+		"body":    "hello from thread",
+		"msgtype": "m.text",
+		// No m.relates_to in raw (can happen after E2EE decryption)
+	}
+	parsed := &event.MessageEventContent{
+		MsgType: event.MsgText,
+		Body:    "hello from thread",
+		RelatesTo: (&event.RelatesTo{}).SetThread(id.EventID("$root123"), id.EventID("$last456")),
+	}
+
+	// Raw extraction should fail
+	gotRaw := extractThreadID(raw)
+	if gotRaw != "" {
+		t.Errorf("expected empty from raw, got %q", gotRaw)
+	}
+
+	// Typed fallback should succeed
+	gotTyped := extractThreadIDFromParsed(parsed)
+	if gotTyped != "$root123" {
+		t.Errorf("expected $root123 from typed fallback, got %q", gotTyped)
+	}
+}