feat(hero): rotate three positioning lines on a 10s cycle

All three lines render in the DOM; CSS drives the fade via data-active.
Reduced-motion users see the first line only (no interval, no fade).
Rotation pauses on hover and keyboard focus. aria-live=off on the
rotator so AT does not announce every swap; aria-hidden flips per-swap
to avoid duplicate heading announcements.

Also set vite.build.assetsInlineLimit=0 in astro.config.mjs so Astro
emits the rotator script as a same-origin external file (dist/assets/)
rather than inlining it — required for CSP script-src 'self' compliance.

astro.config.mjs

@@ -19,6 +19,11 @@ export default defineConfig({
   vite: {
     build: {
       cssMinify: 'lightningcss',
+      // Prevent Astro from inlining small scripts into the HTML.
+      // Without this, the hero rotator script (< 4 KB) gets inlined as a
+      // <script type="module"> tag, which violates CSP script-src 'self'
+      // (no 'unsafe-inline'). Setting 0 forces all scripts to external files.
+      assetsInlineLimit: 0,
     },
   },
 });