feat: update Jan’s client request to adapt API changes from Cortex

[louis-jan]

Describe Your Changes

This PR aims to update the cortex API request regarding the default engine variant. Previously, the settings payload was included in the search parameters, but it’s now correct to include it in the body of the request.

Fixes Issues

• feat: Update Jan’s client request to adapt API changes from Cortex #4123

Changes made

1. API Request Changes:

   • Added explicit JSON payload (version, variant) while posting to the ky.post method to support a legacy API.

2. Test Enhancements:

   • Imports: Added import for fork from the child_process module.
   • Mocks: Implemented a mock for child_process.fork to simulate child process behavior.
   • Test Cases:
     • Updated test descriptions for more clarity.
     • Used mockFork to define behavior for fork mock, especially handling messages for CPU instruction sets.
     • Changed test assertions to use resolves.toEqual or resolves.toBe to handle asynchronous operations with promises.
     • Duplication of logic was reduced by introducing modular mock process handling.

3. General Formatting:

   • Minor string formatting adjustments (e.g., consistent use of single quotes).

These changes focus on improving API interaction robustness and enhancing test reliability through better simulation of asynchronous operations.

[github-actions]

Barecheck - Code coverage report

Total: 69.18%

Your code coverage diff: 0.00% ▴

✅ All code changes are covered

[louis-jan]

Feature build:
https://github.com/janhq/jan/actions/runs/12031021745