fix(dev): proxy content registry to CLI server

Inline spark tables (role=spark-table) live in the content registry, but the
rsbuild dev proxy forwarded only /__COMPLETIONS.json and
/__CONTENT_INDEX.json. The registry fetch fell back to the SPA index.html,
so /roll resolved the inline CSV as HTML and csv-parse failed with an
invalid opening quote.

Load the registry before publishing the loaded completions state so a roll
cannot fire while inline content is still unresolvable.

rsbuild.config.ts

@@ -55,6 +55,7 @@ export default defineConfig({
       // Proxy content API requests to the CLI dev server (npm run tttk)
       "/__CONTENT_INDEX.json": "http://localhost:3000",
       "/__COMPLETIONS.json": "http://localhost:3000",
+      "/__CONTENT_REGISTRY.json": "http://localhost:3000",
       "/content": "http://localhost:3000",
       "/.ttrpg": "http://localhost:3000",
     },