i18n(ar): mirror the layout right to left

- The title, style indicator and both rails swap sides in RTL through logical
  properties (inset-inline-*, margin-inline-*, border-inline-start); LTR
  computes the same values. The Display/Context rail keeps its physical
  `right` for the credit-clearance model and swaps in rtl.css above 720px.
- rtl.css: no letter-spacing on Arabic (it tears joined letters apart);
  Noto Sans Arabic leads the Arabic font stacks so words are not set in a
  fixed-pitch fallback; the intel HUD and cockpit instruments stay a
  left-to-right instrument overlay; media transport and the radio dial stay
  left to right; feed headlines and station names take their own direction;
  the moved rail's arrows flip.
- isolate(): a quantity in RTL text (2.7 كم, -18.0°) is wrapped in
  first-strong isolates so its digits do not join a neighbouring Latin run.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

index.html

@@ -21,7 +21,7 @@
   <link rel="stylesheet" href="/style.css" />
   <link rel="preconnect" href="https://fonts.googleapis.com" />
   <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin />
-  <link href="https://fonts.googleapis.com/css2?family=JetBrains+Mono:wght@300;400;500;600;700&family=Inter:wght@300;400;500;600&display=swap" rel="stylesheet" />
+  <link href="https://fonts.googleapis.com/css2?family=JetBrains+Mono:wght@300;400;500;600;700&family=Inter:wght@300;400;500;600&family=Noto+Sans+Arabic:wght@400;500;600;700&display=swap" rel="stylesheet" />
   <!-- Icon font subset to the glyphs this app renders. Keep `icon_names` in sync
        with the sources: src/materialSymbolsSubset.test.mjs fails when a source
        names a glyph this list is missing, because a missing glyph does not draw