Keep bunext sitemap alive while sitemap exports query the DB

Bun's SQL client (mariadb/mysql adapters, Bun 1.3.14) doesn't keep the
event loop alive for a query on an idle connection, so a second dynamic
route's sitemap export querying the DB made the command exit silently.
Hold the loop open with a timer during generation, and log what a stuck
run is waiting on.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/__tests__/commands/sitemap.test.ts

@@ -217,6 +217,35 @@ describe("bunext sitemap", () => {
         );
     });
 
+    it("waits for sitemap exports that don't keep the event loop alive", async () => {
+        // Like Bun's SQL client querying on an idle connection: the
+        // promise settles, but nothing holds the process open meanwhile.
+        const unrefServerFile = (paths: string[]) =>
+            `export const sitemap = () => new Promise((resolve) => {
+                setTimeout(() => resolve(${JSON.stringify(paths)}), 50).unref();
+            });`;
+
+        writeConfig(`{ origin: "https://example.com" }`);
+        writeProjectFile(
+            "src/pages/blog/[slug].server.ts",
+            unrefServerFile(["/blog/a"]),
+        );
+        writeProjectFile(
+            "src/pages/docs/[slug].tsx",
+            "export default () => null",
+        );
+        writeProjectFile(
+            "src/pages/docs/[slug].server.ts",
+            unrefServerFile(["/docs/a"]),
+        );
+
+        const res = await runSitemap();
+
+        expect(res.exit_code).toBe(0);
+        expect(locs(readOutput())).toContain("https://example.com/blog/a");
+        expect(locs(readOutput())).toContain("https://example.com/docs/a");
+    });
+
     it("exits with code 1 when config additional_paths throws", async () => {
         writeConfig(`{
             sitemap: {