Function try_alloc_kernel_heap 

pub unsafe fn try_alloc_kernel_heap(
    layout: Layout,
) -> Result<*mut u8, KernelHeapAllocError>

Fallible heap entry point with explicit backend-aware errors.

Kernel code that can recover from allocation failure should prefer this API over Box/Vec/GlobalAlloc, which eventually route to alloc_error_handler and remain fatal by language contract.