fix: avoid caching non-positive TTL entries

sdks/javascript/src/cache.ts

@@ -5,7 +5,7 @@
 export interface Cache {
   /** Return a cached value, or `undefined` on miss/expiry. */
   get(key: string): Promise<unknown | undefined>;
-  /** Store a value for the given TTL in milliseconds. */
+  /** Store a value for the given TTL in milliseconds. Non-positive TTL means "do not cache". */
   set(key: string, value: unknown, ttlMs: number): Promise<void>;
   /** Delete one cache entry. */
   delete(key: string): Promise<void>;
@@ -31,6 +31,10 @@ export class MemoryCache implements Cache {
   }
 
   async set(key: string, value: unknown, ttlMs: number): Promise<void> {
+    if (ttlMs <= 0) {
+      this.map.delete(key);
+      return;
+    }
     this.map.set(key, { at: Date.now(), value, ttlMs });
   }