Function heap_validate 

pub unsafe fn heap_validate(ptr: *const u8) -> Result<(), HeapError>

Validate a heap object’s structural integrity.

Checks:

• Non-null pointer
• Valid tag byte
• Non-zero size
• Size consistent with field count
• Closure code_ptr is non-null

Does NOT follow field pointers (use heap_validate_deep for that).

Safety

ptr must point to readable memory of at least size bytes.