fix: document inherited COM interface methods

[nanookclaw]

Summary

Fixes #1391.

Inherited COM interface methods are re-emitted with new, but their documentation lookup used the derived interface name. That made inherited IShellDispatch2 members such as FileRun search for IShellDispatch2.FileRun, even though the docs entry belongs to the declaring base interface, IShellDispatch.FileRun.

This updates the COM interface generator to use the method metadata declaring interface only for inherited members while preserving the existing lookup key for methods declared directly on the generated interface. A focused regression test generates IShellDispatch2, checks that inherited FileRun is still emitted as new void FileRun();, and verifies it receives the same XML docs as IShellDispatch.FileRun. The test also checks a direct IShellDispatch2 method still receives documentation.

Verification

/tmp/dotnet-cswin32/dotnet test test/Microsoft.Windows.CsWin32.Tests/Microsoft.Windows.CsWin32.Tests.csproj --no-restore --filter FullyQualifiedName~COMTests.InheritedCOMInterfaceMethodsUseBaseMethodDocs

[jevansaks]

@nanookclaw thanks for the contribution! Looks good, but there is a merge conflict. Could you resolve and I can approve?

[nanookclaw]

Rebased on current main and force-pushed c1807a5.

Conflict resolution kept the docs fix (apiDocsKey uses the declaring interface for inherited methods) while preserving the new source-generator behavior from main that avoids redeclaring inherited interface members.

Local verification:

• git diff --check
• dotnet restore test/Microsoft.Windows.CsWin32.Tests/Microsoft.Windows.CsWin32.Tests.csproj
• dotnet test test/Microsoft.Windows.CsWin32.Tests/Microsoft.Windows.CsWin32.Tests.csproj --no-restore --filter FullyQualifiedName~COMTests.InheritedCOMInterfaceMethodsUseBaseMethodDocs