API Client Fetch Override

What: Internal enhancement allowing custom fetch implementations to be injected into the API client for testing or custom network handling.

Details:

• The API client factory function (fF()) now accepts an optional fetchOverride parameter
• Replaces previous hardcoded fetch selection logic
• Primarily used internally but enables advanced customization scenarios
• Evidence: fF() at line 376120, fetch override usage at lines 411360 and 432771