Files view: widen the change-details modal again and keep the legend on one row

- modal max-width 900px -> 1100px
- the legend's swatch and label were separate flex children, so a line break
  could split them and the three entries wrapped; each pair is now one
  `.hex-legend-item` (nowrap, no shrink) and the legend itself is
  `flex-wrap: nowrap` with `overflow-x: auto`, so it stays on a single row
- Node test: the modal test now checks the path header and that the legend
  follows the views as three grouped items
- SW cache simtrace-analyser-v70 (cosmetic, no version bump)

frontend/sw.js

@@ -1,4 +1,4 @@
-const CACHE = 'simtrace-analyser-v69';
+const CACHE = 'simtrace-analyser-v70';
 
 const PRECACHE = [
     'index.html',