Document the required ATL and MFC build components

[mikemeerschaert]

Summary

A fresh Visual Studio 2022 Build Tools install with only the Desktop development with C++ workload (Microsoft.VisualStudio.Workload.VCTools --includeRecommended) cannot build OpenTS: code/wonline.cpp includes atlbase.h, which requires Microsoft.VisualStudio.Component.VC.ATL, and code/Sun.rc includes afxres.h, which requires Microsoft.VisualStudio.Component.VC.ATLMFC. Neither component is selected by the workload, and docs/BUILDING.md did not mention them. This change documents both components as build requirements.

Classification

Documentation-only. No engine behavior, interface, or compatibility boundary is affected.

Validation

• Requirement evidence (August 27, 2026; MSVC 19.44.35228, Windows SDK 10.0.26100, CMake 4.4.2): a fresh VS 2022 Build Tools install with only the workload and its recommended components failed to build, first at code/wonline.cpp on the missing atlbase.h and, with ATL added, at code/Sun.rc on the missing afxres.h.
• python manual/tools/manage.py check: extraction, catalog, route, contract, lifecycle, and source-link checks passed with zero catalog deltas. The site-build step did not run because the machine lacks Node/npm.
• No engine build was run for this change itself, as it touches only documentation.

Documentation

• docs/BUILDING.md (owner of build support): adds an ATL and MFC row to the supported-target table, extends the install paragraph with the two components and their unattended-install IDs, and records the evidence in the verification boundary.
• manual/content/using/build-and-run.md: the install sentence now names both components; toolchain detail remains owned by docs/BUILDING.md, which the page links.

[Metadorius]

I don't know how it's done in cmake, but in Visual Studio you can ship a project required components file, could supplement this.

[mikemeerschaert]

Good idea, added in 9462abf. There's now a .vsconfig at the repo root with the workload and both components, and docs/BUILDING.md mentions it, so you can grab everything in one step through the installer's import or an unattended --config install.

About the CMake issue you mentioned: I think Visual Studio looks for a .vsconfig near the open solution or folder, so "Open Folder" on the repo root should work. I'm not totally sure whether it also fires for the generated build/OpenTS.sln, I haven't used visual studio in ages (I switched to VS code a long time ago as i mainly do typescript api work now) and I don't want to install it just to test this. Can you please confirm it shows up for the generated solution? if so, we can update the docs