fix: update search() return type to match v3 response format

Change TS client search() return type from Promise<Array<Memory>>
to Promise<{ results: Array<Memory> }> to match v3 API envelope.
Update unit test mocks to return {results: []} and fix assertions.

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

mem0-ts/src/client/mem0.ts

@@ -280,7 +280,7 @@ export default class MemoryClient {
   async search(
     query: string,
     options?: SearchMemoryOptions,
-  ): Promise<Array<Memory>> {
+  ): Promise<{ results: Array<Memory> }> {
     if (this.telemetryId === "") await this.ping();
     const payloadKeys = Object.keys(options || {});
     this._captureEvent("search", [payloadKeys]);