perf: load the Settings dialog on demand; entry chunk 351.8 → 277.1 kB gzip

Settings (every page, pickers, the denoise tester) was in the entry
chunk though it only renders when opened. Load it lazily behind a
focusable spinner (it opens inside a FocusTrap), and warm the chunk
when the app goes idle. SettingsPages and the status localStorage keys
move to tiny modules so callers don't pull the dialog back in.
sanitize-html (+postcss, htmlparser2) and chroma-js get their own vendor
chunks; with Settings gone the chunk graph had dropped them into the
entry chunk.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5

src/app/features/settings/SettingsLazy.tsx

@@ -0,0 +1,43 @@
+import React, { lazy, Suspense } from 'react';
+import { Box, Spinner, config } from 'folds';
+import type { SettingsPages } from './pages';
+
+// Settings is a large, rarely-open dialog (all its pages, pickers, the
+// denoise tester…). Load it on first open instead of in the entry chunk, and
+// warm the chunk once the app is idle so opening it rarely waits.
+const loadSettings = () => import('./Settings');
+const SettingsDialog = lazy(() => loadSettings().then((m) => ({ default: m.Settings })));
+if (typeof window !== 'undefined') {
+  const warm = () => {
+    loadSettings().catch(() => undefined);
+  };
+  if ('requestIdleCallback' in window) window.requestIdleCallback(warm, { timeout: 10_000 });
+  else setTimeout(warm, 5_000);
+}
+
+type SettingsProps = {
+  initialPage?: SettingsPages;
+  requestClose: () => void;
+};
+
+export function Settings(props: SettingsProps) {
+  return (
+    <Suspense
+      fallback={
+        // Settings opens inside a FocusTrap, which needs a tabbable node.
+        <Box
+          tabIndex={0}
+          role="status"
+          aria-label="Loading settings"
+          alignItems="Center"
+          justifyContent="Center"
+          style={{ padding: config.space.S700, outline: 'none' }}
+        >
+          <Spinner variant="Secondary" size="400" />
+        </Box>
+      }
+    >
+      <SettingsDialog {...props} />
+    </Suspense>
+  );
+}