i18n(ar): own the Arabic catalog in the application package; mirror select chevrons

The application package boundary owns src/i18n/locales/ar.json beside the
other catalogs, and the style.css shim test checks that the shim holds only
import statements rather than counting its lines, so adding rtl.css to it
does not read as rules.

Selects pad the chevron's side with padding-inline-end, as do the Radio
filter, the SDR gain select and the voice timeout select, which set their
own padding; rtl.css moves the chevron to the left, where an Arabic field's
text ends. A rail legend's range keeps left-to-right order under its colour
ramp, which always runs low to high from left to right.

src/ui/rtlLayout.test.mjs

@@ -111,3 +111,38 @@ test('the Space Missions counter reads as a number pair in right-to-left', () =>
   assert.match(counters[1], /\[data-mission-index\]/);
   assert.match(counters[2], /direction: ltr;/);
 });
+
+test('select chevrons and legend ranges follow the field and the ramp in right-to-left', () => {
+  const field = sheet('form-field.css');
+  assert.match(
+    ruleBody(field, 'select.gev-field'),
+    /padding-inline-end: 22px;/,
+  );
+  assert.match(
+    ruleBody(field, 'select.gev-field--compact'),
+    /padding-inline-end: 18px;/,
+  );
+  // Selects that set their own padding keep the chevron's room at the end.
+  for (const [name, selector, inline] of [
+    ['radio.css', '#radio-filter', '8px 24px'],
+    ['radio.css', '.sdr-gain-row select', '7px 22px'],
+    ['voice-card.css', '#gev-voice-timeout-select', '0.45rem 22px'],
+  ]) {
+    const body = ruleBody(sheet(name), selector);
+    assert.match(body, new RegExp(`padding-inline: ${inline};`));
+    assert.doesNotMatch(body, /(?:^|\s)padding(?:-right)?:/);
+  }
+  const rtl = sheet('rtl.css');
+  assert.match(
+    ruleBody(rtl, "html[dir='rtl'] select.gev-field"),
+    /background-position: left 8px center;/,
+  );
+  assert.match(
+    ruleBody(rtl, "html[dir='rtl'] select.gev-field--compact"),
+    /background-position: left 6px center;/,
+  );
+  assert.match(
+    ruleBody(rtl, "html[dir='rtl'] .rail-card-scale"),
+    /direction: ltr;/,
+  );
+});