Moved the explain_exit_code function directly into api.func, removing external dependency loading. Also cleaned up merge conflict markers and unified documentation for diagnostics_check in build.func.
Expanded inline documentation and section headers across misc/api.func, misc/build.func, misc/core.func, misc/error_handler.func, and misc/install.func for improved maintainability and clarity. Refactored error handling to use centralized explain_exit_code and updated API telemetry/reporting logic. Enhanced modularity and structure of utility, validation, and setup functions, and improved comments for user guidance and developer onboarding.
