[pmeems]

Phase 1 of the CMake migration plan: CMake foundation and the MapWinGIS.Core DLL. The MSBuild .slnx build is unchanged and stays the supported build until the later phases land.

Changes

• Root CMakeLists.txt (CMake 3.28+, project(MapWinGIS6 VERSION 6.0.0 LANGUAGES C CXX)), restricted to Debug;Release.
• cmake/MwgVcpkg.cmake: runs before project(). Resolves the vcpkg root (MWG_VCPKG_ROOT, ../vcpkg, VCPKG_ROOT, as bootstrap-vcpkg.ps1 does), pins the triplets, and uses its own install tree vcpkg_installed/cmake-<Platform>. The tests feature follows MWG_BUILD_TESTS.
• cmake/MwgPlatform.cmake: checks MSVC ≥ 19.50 (v145), that the architecture matches the triplet (a fatal error with a CLion hint), and the Windows SDK (pinned for VS, a warning under Ninja).
• cmake/MwgFlagOverrides.cmake and cmake/MwgCompilerOptions.cmake: CMake's MSVC default flags (/DWIN32 /D_WINDOWS ...) are cleared, and mwg_apply_common_options() applies the audited MSBuild options PRIVATE per target. That includes _WINDLL, /JMC, PDBs in Release, and the Win32 defaults /Oy- /analyze- /SAFESEH.
• cmake/MwgRuntimeDeploy.cmake: MapWinGIS.RuntimeData copies share/gdal → gdal-data and share/proj → proj, using a stamp file. It keeps MWG_DEPLOY_RUNTIME_DATA and the missing-data warning.
• src/MapWinGIS.Core/CMakeLists.txt: explicit source lists with source_group(TREE), PUBLIC include/, PRIVATE src/, DEFINE_SYMBOL MWG_CORE_BUILD, and PRIVATE GDAL::GDAL GEOS::geos_c.
• CMakePresets.json: Ninja x64-debug|release and x86-debug|release, plus vs2026-x64|x86 (-T v145), with matching build and test presets. Output goes to out/b/<preset>/bin, never to bin/.
• Parity script: case-insensitive link options, an "explained" list for deliberate link differences, and a warning when a binary was not relinked.
• Docs: CMake section in BUILDING.md, parity status in CMAKE-MIGRATION.md.

Verification

• The parity script reports 0 lost compile/link options and 0 warnings for Core in Debug and Release, x64 and Win32.
• dumpbin: identical dependents, 260 exports, subsystem and DLL characteristics. The embedded manifest is byte-identical.
• The VS presets configure and build (x64 Debug/Release, x86 Debug).
• MSBuild Debug|x64 still builds; 173 tests run (170 pass, 3 skipped as before). The two output trees don't overlap.
• Configure rejects RelWithDebInfo and an architecture/triplet mismatch.

Explained differences

The manifest switches are handled by CMake's link wrapper. vcpkg auto-link is replaced by explicit imported targets. odbc32/odbccp32 are unused MSBuild defaults, and /TLBID:1 only matters for the OCX. The imported targets add /I.../include/geos and, in Debug, GDAL_DEBUG.

Known limitations

• CLion profiles were not verified interactively.
• Ninja cannot pin the Windows SDK.
• The Core tests run under CMake from Phase 3.

Dependencies

Stacked on #39 (Phase 0, cmake-phase-0-audit).