🔌 fix: Isolate Code-Server HTTP Agents to Prevent Socket Pool Contamination (#12311)

* 🔧 fix: Isolate HTTP agents for code-server axios requests

Prevents socket hang up after 5s on Node 19+ when code executor has
file attachments. follow-redirects (axios dep) leaks `socket.destroy`
as a timeout listener on TCP sockets; with Node 19+ defaulting to
keepAlive: true, tainted sockets re-enter the global pool and destroy
active node-fetch requests in CodeExecutor after the idle timeout.

Uses dedicated http/https agents with keepAlive: false for all axios
calls targeting CODE_BASEURL in crud.js and process.js.

Closes #12298

* ♻️ refactor: Extract code-server HTTP agents to shared module

- Move duplicated agent construction from crud.js and process.js into
  a shared agents.js module to eliminate DRY violation
- Switch process.js from raw `require('axios')` to `createAxiosInstance()`
  for proxy configuration parity with crud.js
- Fix import ordering in process.js (agent constants no longer split imports)
- Add 120s timeout to uploadCodeEnvFile (was the only code-server call
  without a timeout)

* ✅ test: Add regression tests for code-server socket isolation

- Add crud.spec.js covering getCodeOutputDownloadStream and
  uploadCodeEnvFile (agent options, timeout, URL, error handling)
- Add socket pool isolation tests to process.spec.js asserting
  keepAlive:false agents are forwarded to axios
- Update process.spec.js mocks for createAxiosInstance() migration

* ♻️ refactor: Move code-server agents to packages/api

Relocate agents.js from api/server/services/Files/Code/ to
packages/api/src/utils/code.ts per workspace conventions. Consumers
now import codeServerHttpAgent/codeServerHttpsAgent from @librechat/api.

packages/api/src/utils/code.ts

@@ -0,0 +1,11 @@
+import http from 'http';
+import https from 'https';
+
+/**
+ * Dedicated agents for code-server requests, preventing socket pool contamination.
+ * follow-redirects (used by axios) leaks `socket.destroy` as a timeout listener;
+ * on Node 19+ (keepAlive: true by default), tainted sockets re-enter the global pool
+ * and kill unrelated requests (e.g., node-fetch in CodeExecutor) after the idle timeout.
+ */
+export const codeServerHttpAgent = new http.Agent({ keepAlive: false });
+export const codeServerHttpsAgent = new https.Agent({ keepAlive: false });

packages/api/src/utils/index.ts

@@ -1,5 +1,6 @@
 export * from './axios';
 export * from './azure';
+export * from './code';
 export * from './common';
 export * from './content';
 export * from './email';