test: fix unit test cases

[Rishavraaj]

This PR focuses on fixing hanging and failing unit tests across the workspace, along with improving the Jest configuration for better stability and centralized mock setups.

🛠️ Changes Made

• Centralized Test Setup for Agents ([NEW] libs/agents/src/test-setup.ts)
  • Created a global test setup file to accurately mock @langchain/openai and provide a functional MockChatOpenAI implementation.
  • Linked the new setup file in libs/agents/jest.config.cts via setupFilesAfterEnv.
  • Added the setup file to tsconfig.lib.json and tsconfig.spec.json for proper compilation.
• Fixed persistent-context.middleware.spec.ts in Agents Library (libs/agents/src/lib/middleware/persistent-context.middleware.spec.ts)
  • Updated the mocked ContactsService to correctly use findById instead of findOne, ensuring the mock aligns with the actual interface.
• Fixed Hanging Tests in Chat Route (apps/web/src/app/api/chat/route.test.ts)
  • Added proper promise resolution and text stream consuming (await response.text()) to prevent tests from hanging on open handles.
  • Consolidated formatting to use double quotes consistently in the file.
• Jest Configuration Updates
  • Updated libs/agents/jest.config.cts to integrate the centralized setup file.
  • Updated libs/sales/jest.config.cts with passWithNoTests: true to prevent test task failures if no specs are present in the sales package.

✅ Verification

• All tests in the workspace now run explicitly via nx run-many -t test.
• No lingering open handles or unhandled promises in the Next.js API route tests.