tui: add tool rendering

cleaned up message rendering and changed cache semantics

other smaller tweaks

pkg/util/tty/highlight.go

@@ -58,3 +58,29 @@ func (s *ChromaHighlighter) HighlightS(text string) (string, error) {
 	s.formatter.Format(&sb, s.style, it)
 	return sb.String(), nil
 }
+
+func (s *ChromaHighlighter) HighlightLang(w io.Writer, text string, lang string) (error) {
+	l := lexers.Get(lang)
+	if l == nil {
+		l = lexers.Fallback
+	}
+	l = chroma.Coalesce(l)
+	old := s.lexer
+	s.lexer = l
+	err := s.Highlight(w, text)
+	s.lexer = old
+	return err
+}
+
+func (s *ChromaHighlighter) HighlightLangS(text string, lang string) (string, error) {
+	l := lexers.Get(lang)
+	if l == nil {
+		l = lexers.Fallback
+	}
+	l = chroma.Coalesce(l)
+	old := s.lexer
+	s.lexer = l
+	highlighted, err := s.HighlightS(text)
+	s.lexer = old
+	return highlighted, err
+}