fix(memory): PoolAllocator::Allocate returns null silently on exhaustion — should assert

[JeanPhilippeKernel]

Summary

PoolAllocator::Allocate() returns nullptr silently when the pool is exhausted. No assertion, no log, no diagnostic.

Location

ZEngine/ZEngine/Core/Memory/Allocator.cpp:237-249

void* PoolAllocator::Allocate()
{
    PoolFreeNode* node = head;
    if (node == nullptr)
        return nullptr;   // silent null — no assert, no log
    ...
}

Detail

Every other failure path in the allocator system uses ZENGINE_VALIDATE_ASSERT. A pool returning null on exhaustion is a capacity-planning failure — callers that skip the null check (e.g. ZPushDynamicArray macro users) will dereference null with no diagnostic.

ArenaAllocator::Resize asserts on OOM. PoolAllocator::Allocate should be consistent.

Fix

void* PoolAllocator::Allocate()
{
    ZENGINE_VALIDATE_ASSERT(head != nullptr, "PoolAllocator::Allocate: pool exhausted — increase capacity at init");
    PoolFreeNode* node = head;
    head = head->Next;
    Helpers::secure_memset(node, 0, chunk_size, chunk_size);
    return node;
}

Impact

Medium — any caller that does not check the return value of ZPushDynamicArray / pool.Allocate() dereferences null silently in all build modes today.