Document Folder APIs and add local Visit Examples.

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

example_test.go

@@ -0,0 +1,51 @@
+package goncfiles_test
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+
+	goncfiles "gitea.neitzel.de/konrad/go-nc-files"
+)
+
+func ExampleOpenLocal() {
+	root := tTempDir()
+	settings := filepath.Join(root, "settings.json")
+	files := filepath.Join(root, "files")
+	_ = os.MkdirAll(files, 0o755)
+
+	visit, err := goncfiles.OpenLocal(files, settings, "myapp", "")
+	if err != nil {
+		fmt.Println("err:", err)
+		return
+	}
+	if err := visit.FS.Write("note.txt", []byte("hi")); err != nil {
+		fmt.Println("write:", err)
+		return
+	}
+	data, err := visit.FS.Read("note.txt")
+	if err != nil {
+		fmt.Println("read:", err)
+		return
+	}
+	fmt.Println(visit.WorkingRel, string(data))
+	// Output: myapp hi
+}
+
+func ExampleLocalFolder() {
+	dir := tTempDir()
+	folder := goncfiles.LocalFolder(dir)
+	_ = folder.Write("a.txt", []byte("x"))
+	ok, _ := folder.Exists("a.txt")
+	fmt.Println(ok)
+	// Output: true
+}
+
+// tTempDir is a tiny helper so examples stay self-contained without testing.T.
+func tTempDir() string {
+	dir, err := os.MkdirTemp("", "goncfiles-example-*")
+	if err != nil {
+		panic(err)
+	}
+	return dir
+}