feat: import agents_and_robots platform as unibots (Matrix-out, unibus transport)

Reemplaza el scaffold del echobot por la plataforma completa de bots traida
desde ~/DataProyects/Github/agents_and_robots tras la operacion Matrix-out:
los bots ya no hablan por Matrix sino por el bus unibus (modelo todo-rooms +
E2E via shell/transportunibus sobre github.com/enmanuel/unibus/pkg/client).

- go.mod: replace de unibus -> ../unibus y de fn-registry -> ../../../.. (paths
  relativos reajustados a la nueva ubicacion dentro de fn_registry).
- app.md: bump a 0.2.0, descripcion + arquitectura + comandos + gotchas reales.
- modulo Go conservado como github.com/enmanuel/agents (sin reescribir imports).

agents_and_robots queda archivado como museo de la era Matrix.

tools/file/file.go

@@ -0,0 +1,54 @@
+package file
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"path/filepath"
+
+	"github.com/enmanuel/agents/internal/config"
+	"github.com/enmanuel/agents/tools"
+)
+
+// NewReadFile creates a read_file tool that reads local files.
+// Deny-by-default: if AllowedPaths is empty, all reads are rejected.
+// Resolves symlinks and normalizes paths to prevent traversal attacks.
+func NewReadFile(cfg config.FileOpsCfg) tools.Tool {
+	return tools.Tool{
+		Def: tools.Def{
+			Name:        "read_file",
+			Description: "Read the contents of a local file.",
+			Parameters: []tools.Param{
+				{Name: "path", Type: "string", Description: "Absolute path to the file to read", Required: true},
+			},
+		},
+		Exec: func(ctx context.Context, args map[string]any) tools.Result {
+			path := tools.GetString(args, "path")
+			if path == "" {
+				return tools.Result{Err: fmt.Errorf("read_file: path is required")}
+			}
+
+			absPath, err := filepath.Abs(path)
+			if err != nil {
+				return tools.Result{Err: fmt.Errorf("read_file: %w", err)}
+			}
+
+			if err := validatePath(absPath, cfg.AllowedPaths); err != nil {
+				return tools.Result{Err: err}
+			}
+
+			data, err := os.ReadFile(absPath)
+			if err != nil {
+				return tools.Result{Err: fmt.Errorf("read_file: %w", err)}
+			}
+
+			// Limit output to 64 KB
+			content := string(data)
+			if len(content) > 64*1024 {
+				content = content[:64*1024] + "\n... (truncated)"
+			}
+
+			return tools.Result{Output: content}
+		},
+	}
+}