Remove unused imports from streamManager.ts

Removed unused imports: fs, path (first occurrence), os
These were left over after switching to execBuffered() for temp dir creation.

Author: ammar-agent

src/services/streamManager.ts

@@ -1,7 +1,4 @@
 import { EventEmitter } from "events";
-import * as fs from "fs";
-import * as path from "path";
-import * as os from "os";
 import {
   streamText,
   stepCountIs,