feat: Mac-like scrollbars - thin, no track, shown while scrolling or at the edge and fading out, none when there is nothing to scroll; a lone terminal's bar sits by the frame, right of the plus

internal/server/web/templates/files.html

@@ -6,6 +6,7 @@
 <title>Файлы · {{.Agent.Name}} - LPRA</title>
 <link rel="stylesheet" href="{{asset "app.css"}}">
 <script src="{{asset "pin.js"}}"></script>
+<script src="{{asset "scroll.js"}}" defer></script>
 <link rel="stylesheet" href="{{asset "codemirror/codemirror.css"}}">
 <style>
   .fm-bar { display:flex; gap:8px; align-items:center; flex-wrap:wrap; margin-bottom:12px; }