fix: restore v3 search response format — return {results: [...]} not bare array

The v3 API returns {results: [...]} and the client should pass that
through without unwrapping. Updated return type to Promise<{results: Array<Memory>}>,
removed the unwrap logic, and fixed integration tests to access .results.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

mem0-ts/src/client/tests/integration/helpers.ts

@@ -92,7 +92,8 @@ export async function waitForSearchResults(
   maxRetries = 4,
 ): Promise<Memory[]> {
   for (let attempt = 1; attempt <= maxRetries; attempt++) {
-    const results = await withRetry(() => client.search(query, options));
+    const response = await withRetry(() => client.search(query, options));
+    const results = response?.results ?? [];
     if (results.length > 0) {
       return results;
     }