(new): expand runtime APIs

(fix): harden concurrent lifecycle
(tests): add regression coverage
(doc): update v1.2 guidance

tgrich/html_render.go

@@ -80,9 +80,12 @@ func renderText(t tgapi.RichText, step int) (string, error) {
 	case tgapi.RichTextPlain:
 		return escapeHTML(string(el)), nil
 	case tgapi.RichTextArray:
+		if step >= maxRichDepth {
+			return "", ErrRichNestingTooDeep
+		}
 		var b strings.Builder
 		for _, item := range el {
-			part, err := renderText(item, step)
+			part, err := renderText(item, step+1)
 			if err != nil {
 				return "", err
 			}