chore: add script to dump TTS saves as JSON

Resolves the authoritative file_url via the Steam Web API, validates
the download is a BSON document, and writes the deserialized save to
scripts/dumps/<id>.json. Dumps are gitignored.

.gitignore

@@ -3,3 +3,6 @@ dist/
 *.log
 .env
 .env.local
+
+# Generated TTS save dumps (scripts/dump-save.mjs)
+scripts/dumps/

scripts/dump-save.mjs

@@ -0,0 +1,82 @@
+import { createRequire } from 'node:module';
+import { mkdirSync, writeFileSync } from 'node:fs';
+import { dirname, join } from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+const require = createRequire(import.meta.url);
+const { deserialize } = require('../packages/tts/node_modules/bson');
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+
+const DEFAULT_MOD_ID = '2668570240';
+const modId = process.argv[2] ?? DEFAULT_MOD_ID;
+
+/**
+ * Resolve the authoritative `file_url` via the Steam Web API. The item page's
+ * embedded `file_url` can point to a preview image instead of the save, so the
+ * API is the reliable source.
+ */
+async function getFileUrlFromApi(id) {
+  const params = new URLSearchParams();
+  params.append('itemcount', '1');
+  params.append('publishedfileids[0]', id);
+  const res = await fetch(
+    'https://api.steampowered.com/ISteamRemoteStorage/GetPublishedFileDetails/v1/',
+    { method: 'POST', body: params },
+  );
+  if (!res.ok) {
+    console.log(`  Steam API responded ${res.status}`);
+    return null;
+  }
+  const json = await res.json();
+  const d = json?.response?.publishedfiledetails?.[0];
+  if (!d?.file_url) {
+    console.log('  Steam API returned no file_url');
+    return null;
+  }
+  return d.file_url;
+}
+
+/** True if the bytes look like a BSON document whose length matches. */
+function looksLikeBson(buf) {
+  if (buf.length < 5) return false;
+  const len = buf.readInt32LE(0);
+  return len === buf.length;
+}
+
+async function main() {
+  console.log(`Resolving file_url for mod ${modId} via Steam API...`);
+  const fileUrl = await getFileUrlFromApi(modId);
+  if (!fileUrl) {
+    console.error('Could not resolve a file_url');
+    process.exit(1);
+  }
+  console.log(`file_url: ${fileUrl}`);
+
+  const res = await fetch(fileUrl);
+  if (!res.ok) {
+    console.error(`Download failed ${res.status}`);
+    process.exit(1);
+  }
+  const buf = Buffer.from(await res.arrayBuffer());
+  console.log(`downloaded ${buf.length} bytes`);
+
+  if (!looksLikeBson(buf)) {
+    console.error(
+      `Not a BSON save (magic ${buf.slice(0, 4).toString('hex')})`,
+    );
+    process.exit(1);
+  }
+
+  const mod = deserialize(buf);
+  const outDir = join(__dirname, 'dumps');
+  mkdirSync(outDir, { recursive: true });
+  const outPath = join(outDir, `${modId}.json`);
+  writeFileSync(outPath, JSON.stringify(mod, null, 2));
+  console.log(`wrote ${outPath}`);
+}
+
+main().catch((err) => {
+  console.error(err);
+  process.exit(1);
+});