Side panel: scrollbar matches the APDU list's width

- the side panel had no scrollbar rule of its own, so it fell back to the
  global 6px default while the APDU list uses 12px; the two now share one
  rule (width 12px, thumb radius 6px = half the bar), so they cannot drift
  apart again — the other panes keep the thin global bar
- Node test pins the shared rule (and the 6px global default)
- SW cache simtrace-analyser-v74 (cosmetic, no version bump)

frontend/index.html

@@ -120,8 +120,10 @@ body { font: 14px/1.5 system-ui, sans-serif; background: var(--bg); color: var(-
 
 /* APDU list */
 .apdu-list { flex: 1 1 0; min-height: 0; overflow-y: auto; padding: 8px; }
-.apdu-list::-webkit-scrollbar { width: 12px; }
+.apdu-list::-webkit-scrollbar,
-.apdu-list::-webkit-scrollbar-thumb { border-radius: 6px; }
+.side-panel::-webkit-scrollbar { width: 12px; }
+.apdu-list::-webkit-scrollbar-thumb,
+.side-panel::-webkit-scrollbar-thumb { border-radius: 6px; }
 .apdu-entry { display: flex; gap: 12px; padding: 3px 12px; border-bottom: 1px solid var(--bg-panel); cursor: pointer; align-items: baseline; }
 .apdu-entry.apdu-pair { background: var(--pair-row); }
 .apdu-entry:hover { background: var(--bg-panel); }

frontend/sw.js

@@ -1,4 +1,4 @@
-const CACHE = 'simtrace-analyser-v73';
+const CACHE = 'simtrace-analyser-v74';
 
 const PRECACHE = [
     'index.html',

frontend/tests/style.test.js

@@ -0,0 +1,22 @@
+// Scrollbar styling: the APDU list and the side panel share one rule, so
+// their widths cannot drift apart (the side panel used to fall back to the
+// global 6px bar while the list uses 12px).
+
+const { test } = require('node:test');
+const assert = require('node:assert');
+const { loadSrc } = require('./helpers.js');
+
+const src = loadSrc();
+
+test('the APDU list and the side panel share the 12px scrollbar rule', () => {
+	const rule = /\.apdu-list::-webkit-scrollbar,\s*\n\.side-panel::-webkit-scrollbar \{ width: 12px; \}/;
+	assert.match(src, rule);
+	// the thumb radius pairs with the width (6px = half of 12px)
+	assert.match(
+		src,
+		/\.apdu-list::-webkit-scrollbar-thumb,\s*\n\.side-panel::-webkit-scrollbar-thumb \{ border-radius: 6px; \}/);
+});
+
+test('the global scrollbar default stays thin for the other panes', () => {
+	assert.match(src, /::-webkit-scrollbar \{ width: 6px; \}/);
+});