Add goTool autotest with bench configs and UART scenarios.

JSON configs describe network and node MACs; scenarios run command
sequences with expect checks. Share UART client API across CLI and tests.

Co-authored-by: Cursor <cursoragent@cursor.com>

goTool/autotest/paths.go

@@ -0,0 +1,79 @@
+package autotest
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+const (
+	ConfigDir   = "testdata/configs"
+	ScenarioDir = "testdata/scenarios"
+)
+
+func ResolveConfigPath(name string) (string, error) {
+	return resolveJSON(name, ConfigDir)
+}
+
+func ResolveScenarioPath(name string) (string, error) {
+	return resolveJSON(name, ScenarioDir)
+}
+
+func resolveJSON(name, dir string) (string, error) {
+	if name == "" {
+		return "", fmt.Errorf("empty name")
+	}
+	if filepath.Ext(name) == ".json" {
+		if fileExists(name) {
+			return name, nil
+		}
+	}
+	base := name
+	if filepath.Ext(base) != ".json" {
+		base += ".json"
+	}
+	for _, root := range configRoots() {
+		p := filepath.Join(root, dir, base)
+		if fileExists(p) {
+			return p, nil
+		}
+	}
+	return "", fmt.Errorf("not found: %s (searched %s under gotool)", base, dir)
+}
+
+func configRoots() []string {
+	var roots []string
+	if wd, err := os.Getwd(); err == nil {
+		roots = append(roots, wd)
+	}
+	// When run from repo root via make.
+	roots = append(roots, "goTool", filepath.Join("..", "goTool"))
+	return roots
+}
+
+func fileExists(path string) bool {
+	st, err := os.Stat(path)
+	return err == nil && !st.IsDir()
+}
+
+func ListJSONFiles(dir string) ([]string, error) {
+	for _, root := range configRoots() {
+		p := filepath.Join(root, dir)
+		entries, err := os.ReadDir(p)
+		if err != nil {
+			continue
+		}
+		var names []string
+		for _, e := range entries {
+			if e.IsDir() || filepath.Ext(e.Name()) != ".json" {
+				continue
+			}
+			names = append(names, strings.TrimSuffix(e.Name(), ".json"))
+		}
+		if len(names) > 0 {
+			return names, nil
+		}
+	}
+	return nil, fmt.Errorf("directory %s not found", dir)
+}