feat(ui): give every panel one scrollbar, select and slider skin

Every scrolling surface carries the kit's .ui-scroll, which
draws the thin themed scrollbar from --scroll-thumb and --scroll-track; the
Context panel and others drew the platform's light scrollbar because the
page declares no dark color-scheme. The per-panel scrollbar rules go; Cyber
sets the two tokens and Cockpit's HUD windows keep their accent tint.

Selects draw .gev-field's own chevron instead of the platform arrow, the
voice selects join .gev-field, number fields keep dark spinners, and the
Street Level range uses the shared slider in its green.

src/ui/cyberTheme.test.mjs

@@ -22,10 +22,14 @@ test('CCTV and Context keep their headers outside Cyber-only scroll bodies', ()
       new URL(`./views/${file}`, import.meta.url),
       'utf8',
     );
-    assert.match(markup, /class="cyber-panel-body" data-rail-scroller/);
+    // The body wears the shared scrollbar skin where Cyber makes it scroll.
+    assert.match(
+      markup,
+      /class="cyber-panel-body ui-scroll" data-rail-scroller/,
+    );
     assert.ok(
       markup.indexOf('class="panel-header"') <
-        markup.indexOf('class="cyber-panel-body"'),
+        markup.indexOf('class="cyber-panel-body ui-scroll"'),
     );
   }
   const shared = readFileSync(