feat: return workshop metadata with mod details

Include the Workshop title and preview image in the items response so the mod header survives a page refresh, not just navigation from search. Resolve both from the same Steam API call.

packages/tts/src/index.ts

@@ -1,5 +1,5 @@
 import { deserialize } from 'bson';
-import type { TTSMod } from '@tts/shared';
+import type { ModDetails, TTSMod } from '@tts/shared';
 import { ItemNotFoundError, NoFileError, SteamApiError } from './errors.js';
 
 const STEAM_API_URL =
@@ -36,6 +36,30 @@ export async function fetchMod(id: string, apiKey: string): Promise<TTSMod> {
   return fetchModFromUrl(fileUrl);
 }
 
+/**
+ * Fetch a save plus its Workshop metadata (title, preview image) in one call.
+ * The metadata comes from the same Steam API request that resolves the save
+ * URL, so it costs no extra round-trip.
+ *
+ * @param id Workshop item ID (digits only).
+ * @param apiKey Steam Web API key.
+ */
+export async function fetchModDetails(
+  id: string,
+  apiKey: string,
+): Promise<ModDetails> {
+  const details = await getPublishedFileDetails(id, apiKey);
+  if (!details.file_url) {
+    throw new NoFileError(id);
+  }
+  const mod = await fetchModFromUrl(details.file_url);
+  return {
+    mod,
+    title: details.title,
+    previewImageUrl: details.preview_url,
+  };
+}
+
 /**
  * Download a TTS save from a direct URL and BSON-deserialize it.
  *
@@ -94,6 +118,18 @@ async function downloadSave(fileUrl: string): Promise<ArrayBuffer> {
 
 /** Resolve the `file_url` for a Workshop item via the Steam API. */
 async function getFileUrl(id: string, apiKey: string): Promise<string> {
+  const details = await getPublishedFileDetails(id, apiKey);
+  if (!details.file_url) {
+    throw new NoFileError(id);
+  }
+  return details.file_url;
+}
+
+/** Fetch the Steam published-file details for a Workshop item. */
+async function getPublishedFileDetails(
+  id: string,
+  apiKey: string,
+): Promise<SteamPublishedFileDetails> {
   const params = new URLSearchParams();
   params.append('key', apiKey);
   params.append('itemcount', '1');
@@ -112,10 +148,7 @@ async function getFileUrl(id: string, apiKey: string): Promise<string> {
   if (!details) {
     throw new ItemNotFoundError(id);
   }
-  if (!details.file_url) {
-    throw new NoFileError(id);
-  }
-  return details.file_url;
+  return details;
 }
 
 export * from './errors.js';