refactor: mover tools a subpackages individuales

Cada tool ahora vive en su propio subpackage dentro de tools/ (clock, file,
http, knowledgetools, matrix, memorytools, ssh, weather) en lugar de archivos
planos en el paquete raíz tools/. Esto mejora la organización, permite imports
selectivos y reduce acoplamiento entre tools. El paquete tools/ raíz conserva
los tipos base (Def, Param, Result, ToolFunc, Tool, Registry).

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

tools/matrix/matrix.go

@@ -0,0 +1,42 @@
+package matrix
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/enmanuel/agents/tools"
+)
+
+// MatrixSender is the interface for sending Matrix messages.
+// Satisfied by shell/matrix.Client.
+type MatrixSender interface {
+	SendText(ctx context.Context, roomID, text string) error
+	SendMarkdown(ctx context.Context, roomID, markdown string) error
+}
+
+// NewMatrixSend creates a matrix_send tool that sends a message to a Matrix room.
+func NewMatrixSend(sender MatrixSender) tools.Tool {
+	return tools.Tool{
+		Def: tools.Def{
+			Name:        "matrix_send",
+			Description: "Send a text message to a Matrix room.",
+			Parameters: []tools.Param{
+				{Name: "room_id", Type: "string", Description: "The Matrix room ID to send to", Required: true},
+				{Name: "message", Type: "string", Description: "The text message to send", Required: true},
+			},
+		},
+		Exec: func(ctx context.Context, args map[string]any) tools.Result {
+			roomID := tools.GetString(args, "room_id")
+			message := tools.GetString(args, "message")
+			if roomID == "" || message == "" {
+				return tools.Result{Err: fmt.Errorf("matrix_send: room_id and message are required")}
+			}
+
+			if err := sender.SendMarkdown(ctx, roomID, message); err != nil {
+				return tools.Result{Err: fmt.Errorf("matrix_send: %w", err)}
+			}
+
+			return tools.Result{Output: fmt.Sprintf("message sent to %s", roomID)}
+		},
+	}
+}