fix(publish-dialog): show Space URL instead of /published/<doc> path

The success state used to display `Live at /published/default` and link
to `/published/default/index.html`, surfacing an implementation detail
of the publisher pipeline (used internally for PDF rendering and
og:image) rather than the canonical URL readers actually visit.

When a published article exists, the backend serves it at the Space
root (`app.get("*")` in `create-app.ts`). Switch the modal to surface
`window.location.origin` instead, both for the displayed URL and the
"View published article" link target.

Made-with: Cursor

frontend/src/components/PublishDialog.tsx

@@ -145,8 +145,14 @@ export const PublishDialog = forwardRef<HTMLDialogElement, Props>(function Publi
     }
   }, [stageEvent, state]);
 
-  const publishedUrl = `/published/${docName}/index.html`;
-  const displayUrl = publishedUrl.replace(/\/index\.html$/, "");
+  // Readers land on the Space root: when a published article exists,
+  // `backend/src/create-app.ts` (`app.get("*")`) serves it at `/`. The
+  // `/published/<docName>/...` path is an implementation detail used by
+  // the publisher pipeline (PDF generation, og:image, ...), not the
+  // canonical reader URL. So we surface the Space URL itself.
+  const origin = typeof window !== "undefined" ? window.location.origin : "";
+  const publishedUrl = origin ? `${origin}/` : "/";
+  const displayUrl = origin || "/";
 
   return (
     <dialog