feat(docs): generate sitemap dynamically using build entry point

Replace the static sitemap.xml with dynamic generation via the new
`build` entry point. The sitemap is now derived from the route
definitions, ensuring it stays in sync as pages are added or removed.

Also adds `outDir` to `BuildEntryContext` so build entries know where
to write additional output files.

https://claude.ai/code/session_01D7p4ghgU7hqJA6SnMfVtPA

Author: claude

packages/docs/public/sitemap.xml

@@ -0,0 +1,43 @@
+import { writeFile } from "node:fs/promises";
+import path from "node:path";
+import type { BuildEntryFunction } from "@funstack/static/build-entry";
+import type { RouteDefinition } from "@funstack/router/server";
+import { routes } from "./App";
+
+const siteUrl = "https://static.funstack.work";
+
+function collectPaths(routes: RouteDefinition[]): string[] {
+  const paths: string[] = [];
+  for (const route of routes) {
+    if (route.children) {
+      paths.push(...collectPaths(route.children));
+    } else if (route.path !== undefined && route.path !== "*") {
+      paths.push(route.path);
+    }
+  }
+  return paths;
+}
+
+function generateSitemap(paths: string[]): string {
+  const urls = paths
+    .map((p) => {
+      const loc = p === "/" ? siteUrl + "/" : `${siteUrl}${p}`;
+      return `  <url>\n    <loc>${loc}</loc>\n  </url>`;
+    })
+    .join("\n");
+
+  return `<?xml version="1.0" encoding="UTF-8"?>
+<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
+${urls}
+</urlset>
+`;
+}
+
+export default (async ({ build, outDir }) => {
+  const paths = collectPaths(routes);
+
+  await Promise.all([
+    build(),
+    writeFile(path.join(outDir, "sitemap.xml"), generateSitemap(paths)),
+  ]);
+}) satisfies BuildEntryFunction;

packages/docs/src/build.ts

@@ -14,6 +14,7 @@ export default defineConfig(async () => {
       funstackStatic({
         entries: "./src/entries.tsx",
         ssr: true,
+        build: "./src/build.ts",
       }),
       {
         // to make .mdx loading lazy

packages/docs/vite.config.ts

@@ -79,7 +79,7 @@ export async function buildApp(
   }
 
   if (entry.buildEntry) {
-    await entry.buildEntry({ build: doBuild });
+    await entry.buildEntry({ build: doBuild, outDir: baseDir });
   } else {
     await doBuild();
   }

packages/static/src/build/buildApp.ts

@@ -8,6 +8,11 @@ export interface BuildEntryContext {
    * You can run additional work before, after, or in parallel with this function.
    */
   build: () => Promise<void>;
+  /**
+   * Absolute path to the output directory where built files are written.
+   * Use this to write additional files (e.g. sitemap.xml) alongside the build output.
+   */
+  outDir: string;
 }
 
 /**