Standardize desktop GLFW/GLEW on vcpkg; fix CMake FetchContent warnings

[trailcode]

Summary

• Standardize desktop MSVC GLFW/GLEW on vcpkg (vcpkg.json + toolchain); remove NuGet and thirdParty/ path glue so local matches CI.
• Silence CMake 4.x FetchContent / policy warnings (CMP0135, MakeAvailable(lua), pybind11 policy floor, googletest v1.15.2).
• Link glfw/GLEW PUBLIC on EzyCad_lib so ImGui backends resolve GLFW/glfw3.h.

Closes #257

Test plan

• Configure with -DCMAKE_TOOLCHAIN_FILE=%VCPKG_ROOT%/scripts/buildsystems/vcpkg.cmake + OCCT 8 paths (match generator to IDE: VS 17 or 18).
• Confirm configure without vcpkg toolchain fails clearly on MSVC.
• Build EzyCad_lib / EzyCad (RelWithDebInfo); run briefly.
• Confirm glfw3.dll / glew32.dll staged next to the exe.
• CI windows-msvc.yml green (already vcpkg-based).
• WASM path still independent of desktop GLFW/GLEW packages.

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Note

Medium Risk
Build and runtime dependency acquisition for all Windows desktop developers changes (vcpkg required); misconfigured local setups will fail configure until the toolchain is set correctly.

Overview
Desktop MSVC builds now get GLFW and GLEW only through the repo vcpkg.json manifest and -DCMAKE_TOOLCHAIN_FILE=.../vcpkg.cmake, matching CI. The NuGet install/link/copy glue under thirdParty/ is removed; configure fails with a clear message if MSVC is used without vcpkg.

CMake finds glfw/GLEW via vcpkg CONFIG packages (with MODULE fallback on non-MSVC), links them PUBLIC on EzyCad_lib so ImGui GLFW/OpenGL backends compile, and stages glfw3.dll / glew32.dll (and debug glew32d.dll) from vcpkg install roots into Release/Debug output dirs. Test targets no longer duplicate GLFW links. FetchContent tweaks: CMP0135, policy floor for pybind11 on CMake 3.31+, FetchContent_MakeAvailable(lua) instead of Populate, googletest bumped to v1.15.2. .gitignore adds /vcpkg_installed.

Docs (README, local-dev, building-occt, third_party/README, CHANGELOG) now describe vcpkg prerequisites instead of NuGet; OCCT still comes from prebuilts, not vcpkg.

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