perf(markdown): load katex css lazily via local FullMarkdown wrapper

core-ui no longer bundles katex.min.css (it would base64-inline ~1.4MB
of fonts into the render-blocking global css). Wrap FullMarkdown locally
to co-locate the katex stylesheet so it loads only in the routes that
render math.

src/components/full-markdown/index.tsx

@@ -0,0 +1,12 @@
+// Wrapper around core-ui's FullMarkdown that co-locates the KaTeX stylesheet.
+//
+// core-ui deliberately does NOT bundle katex.min.css (importing it there
+// base64-inlines ~1.4MB of fonts into the shared, render-blocking index.css).
+// Importing it here keeps the KaTeX CSS in the route chunk that actually
+// renders math, so it loads lazily and never blocks first paint.
+//
+// Always import FullMarkdown from this module, not from '@gpustack/core-ui/markdown'.
+import { FullMarkdown } from '@gpustack/core-ui/markdown';
+import 'katex/dist/katex.min.css';
+
+export default FullMarkdown;