docs: fix redirects for old /latest URLs and root page

Generate latest alias pages for all docs across versions so old URLs
like /latest/en/introduction get proper redirects to the quickstart.
Add root index.astro redirect instead of relying on empty HTML + _redirects.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: cecilia-marques

apps/docs/client/src/pages/[version]/[locale]/[...slug].astro

@@ -24,18 +24,30 @@ export async function getStaticPaths() {
       params: { version: "latest", locale },
       props: { doc: null, version: "latest" },
     })),
-    // "latest" alias for all latest docs (so /latest/en/... redirects to /deco-studio/en/...)
+    // "latest" alias for all docs across all versions (so old /latest/en/... URLs redirect properly)
     ...allDocs
-      .filter((doc) => doc.id.startsWith(`${LATEST_VERSION.id}/`))
-      .map((doc) => {
+      .flatMap((doc) => {
         const parts = doc.id.split("/");
         const locale = parts[1];
         const slug = parts.slice(2).join("/");
+        // Check if this slug exists in the latest version
+        const existsInLatest = allDocs.some(
+          (d) => d.id === `${LATEST_VERSION.id}/${locale}/${slug}`,
+        );
         return {
           params: { version: "latest", locale, slug },
-          props: { doc: null, version: "latest" },
+          props: { doc: null, version: "latest", existsInLatest },
         };
-      }),
+      })
+      // Deduplicate by locale+slug (same slug may exist in multiple versions)
+      .filter(
+        (entry, index, arr) =>
+          arr.findIndex(
+            (e) =>
+              e.params.locale === entry.params.locale &&
+              e.params.slug === entry.params.slug,
+          ) === index,
+      ),
 
     // Actual versioned paths
     ...VERSION_IDS.flatMap((version) => [
@@ -72,15 +84,15 @@ export async function getStaticPaths() {
   ];
 }
 
-const { doc, version: propVersion } = Astro.props;
+const { doc, version: propVersion, existsInLatest } = Astro.props;
 const slug = Astro.params.slug;
 
 // Redirect "latest" alias to actual version
 if (version === "latest") {
-  const target = slug
-    ? `/${LATEST_VERSION.id}/${lang}/${slug}`
-    : `/${LATEST_VERSION.id}/${lang}/studio/quickstart`;
-  return Astro.redirect(target);
+  if (slug && existsInLatest) {
+    return Astro.redirect(`/${LATEST_VERSION.id}/${lang}/${slug}`);
+  }
+  return Astro.redirect(`/${LATEST_VERSION.id}/${lang}/${LATEST_VERSION.root}`);
 }
 
 // Legacy redirects

apps/docs/client/src/pages/index.astro

@@ -0,0 +1,5 @@
+---
+import { LATEST_VERSION } from "../config/versions";
+
+return Astro.redirect(`/${LATEST_VERSION.id}/en/${LATEST_VERSION.root}`);
+---