Enable native arm64 macOS build

[pdaddyo]

Summary

The bundled deps/osx libraries are x86_64-only and the macOS port had bit-rotted against modern Apple Clang. These changes let the engine, tools, and editor build and run natively on Apple Silicon (arm64), and document the process.

Build fixes

• byte_serializer: add long / unsigned long operator<</>> overloads on Apple — under LP64 size_t is distinct from uint64_t (which is long long there), so serializing a size_t was otherwise unmatched
• os_mac: parseProgramPath returns the full executable path so the caller's parentPath() resolves the asset dir correctly (was one level too high)
• opengl: guard glObjectLabel calls — it's null on macOS OpenGL 4.1 (no KHR_debug)
• zlib/zutil: don't define the classic-Mac fdopen stub on modern macOS, where TARGET_OS_MAC is always 1
• avf: update MovieAPI / MoviePlayer signatures to take const HalleyAPI&, matching the current base interface
• shader_importer_dxc: guard D3D12-only code behind _MSC_VER
• vector_test: add typename on dependent types (required by Apple Clang)
• cmake: link Security + CoreFoundation (needed for httplib TLS) on Apple

Docs

• README: native Apple Silicon build instructions — Homebrew dependencies, building ShaderConductor from source (no arm64 prebuilt), and the macOS CMake configure invocation

Notes

• A full Apple Silicon build also needs an arm64 ShaderConductor built from source (no upstream prebuilt) and Homebrew deps; both documented in the README.
• Known issue, not addressed here: GL shader-reflection warnings ("Could not find uniform block HalleyBlock") when using a from-source ShaderConductor, whose newer SPIRV-Cross emits GLSL differently than the engine's GL reflection expects.

Opening as a draft for review.