fix(memory): prevent server OOM from unbounded Next.js fetch cache and dataset info cache

- Add `cache: "no-store"` to fetchParquetFile, fetchJson, and tasks.jsonl fetch
so Next.js does not accumulate large parquet ArrayBuffers in its Data Cache
across many requests over days of continuous operation
- Cap datasetInfoCache at 200 entries with FIFO eviction to prevent unbounded growth

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

src/app/[org]/[dataset]/[episode]/fetch-data.ts

@@ -363,7 +363,7 @@ async function getEpisodeDataV2(
   if (!task && allData.length > 0) {
     try {
       const tasksUrl = buildVersionedUrl(repoId, version, "meta/tasks.jsonl");
-      const tasksResponse = await fetch(tasksUrl);
+      const tasksResponse = await fetch(tasksUrl, { cache: "no-store" });
 
       if (tasksResponse.ok) {
         const tasksText = await tasksResponse.text();

src/utils/parquetUtils.ts

@@ -25,7 +25,7 @@ export interface DatasetMetadata {
 }
 
 export async function fetchJson<T>(url: string): Promise<T> {
-  const res = await fetch(url);
+  const res = await fetch(url, { cache: "no-store" });
   if (!res.ok) {
     throw new Error(
       `Failed to fetch JSON ${url}: ${res.status} ${res.statusText}`,
@@ -43,7 +43,7 @@ export function formatStringWithVars(
 
 // Fetch and parse the Parquet file
 export async function fetchParquetFile(url: string): Promise<ArrayBuffer> {
-  const res = await fetch(url);
+  const res = await fetch(url, { cache: "no-store" });
 
   if (!res.ok) {
     throw new Error(`Failed to fetch ${url}: ${res.status} ${res.statusText}`);

src/utils/versionUtils.ts

@@ -31,12 +31,13 @@ export interface DatasetInfo {
   features: Record<string, FeatureInfo>;
 }
 
-// In-memory cache for dataset info (5 min TTL)
+// In-memory cache for dataset info (5 min TTL, max 200 entries)
 const datasetInfoCache = new Map<
   string,
   { data: DatasetInfo; expiry: number }
 >();
 const CACHE_TTL_MS = 5 * 60 * 1000;
+const CACHE_MAX_SIZE = 200;
 
 export async function getDatasetInfo(repoId: string): Promise<DatasetInfo> {
   const cached = datasetInfoCache.get(repoId);
@@ -72,6 +73,10 @@ export async function getDatasetInfo(repoId: string): Promise<DatasetInfo> {
       );
     }
 
+    if (datasetInfoCache.size >= CACHE_MAX_SIZE) {
+      // Evict the oldest entry (Maps preserve insertion order)
+      datasetInfoCache.delete(datasetInfoCache.keys().next().value!);
+    }
     datasetInfoCache.set(repoId, {
       data: data as DatasetInfo,
       expiry: Date.now() + CACHE_TTL_MS,