Endian-aware native pointer readers instantiate the wrong pointer type #188

The endian-aware pointer readers in include/cpp/marshal/Marshal.hpp call readPointer<T*> even though readPointer already returns cpp::Pointer. Instantiating the reader therefore produces Pointer<T*> where the declared return type is Pointer.

A compile-only probe against checkout 8d3b460 reproduces this on Linux x86_64 with g++ and HXCPP_API_LEVEL=500:

#include <hxcpp.h>
void probe(const cpp::marshal::View<uint8_t>& bytes) {
    auto p = cpp::marshal::Marshal::readLittleEndianPointer<int>(bytes);
    (void)p;
}

The diagnostic is:

could not convert ... from Pointer<int*> to Pointer<int>

Both readLittleEndianPointer and readBigEndianPointer use the extra pointer level, including their byte-swapping branches. Header inclusion alone does not instantiate these templates, so ordinary builds can miss the problem.

Call readPointer for a pointer-to-T result. Also verify that byte swapping acts on the native pointer representation rather than assuming cpp::Pointer's wrapper representation is the serialized data format. The write methods already operate on value.ptr.

Add compile and round-trip tests that instantiate both endian readers with concrete pointee types. Cover the host-endian and opposite-endian branches. A big-endian hardware run has not been performed here.