Move the build to the stable Visual Studio 2027 and .NET 11 before general availability #181

PostSharp 2027.0 is built and tested on pre-release toolchains, which Documentation/PlatformSupport.md allows only while the product is itself pre-release. Before general availability (2027-01-01), every literal must name a stable build.

Visual Studio 2027 stable (November 2026). Drop the -insiders tag in:

• eng/src/Program.cs (VisualStudioBuildToolsComponentVersion.v18_11, the Preview-channel entry);
• Build/Scripts/common.ps1 ($PostSharpDefaultVisualStudioVersion);
• eng/src/TeamCity/VisualStudioVersion.cs (Vs1811), then Build.ps1 generate-scripts;
• the prose in CLAUDE.md, Build/Scripts/CLAUDE.md, eng/docker/CLAUDE.md and Documentation/BuildInfrastructure.md.

.NET 11 GA (November 2026). Replace 11.0.100-rc.1.26425.128 and 11.0.0-rc.1.26425.128 in Root.Defs.props, global.json, eng/src/global.json, eng/src/Program.cs (then regenerate the Dockerfiles), Tests/TestingFramework/Testing/Runtime/runone.sh unless that directory is deleted first, and Documentation/BuildInfrastructure.md. Install the released SDK on the macOS agent apple-m2, and re-check NetCoreConstants.MaximumSupportedSdkMinorVersion.

Do #110 (the Windows ARM64 build-test cell) in the same pass.

Recorded as items 1, 2 and 12 of Documentation/PB-2027.0-TODO.md.

-- Claude for Gael