Rename the toolchain commands to rb msvc enable/exec

[hsbt]

The MSVC build-environment activation shipped as a top-level rb exec (and its companion rb enable), but exec at the top level reads as "run a command under the selected ruby", the meaning it carries in version managers such as rbenv exec and mise exec. That connotation hides what the command actually does, which is activate an installed Visual Studio or Build Tools MSVC toolchain so native gems can build.

This namespaces both surfaces under the toolset name as rb msvc enable [shell] and rb msvc exec <command...>, and renames the implementation class and file from Devkit to Msvc to match. The word "devkit" is not a Visual Studio term, so the class comment and the design note now describe the mechanism in Visual Studio vocabulary (the MSVC toolset and VsDevCmd.bat, the script behind the Developer Command Prompt). Behavior is unchanged. Only the command spelling, the class name, and the docs move.

# activate the toolchain in the current shell
rb msvc enable powershell | Invoke-Expression

# or run a single build command with the toolchain applied
rb msvc exec gem install nokogiri

[Copilot]

Pull request overview

This PR renames the MSVC toolchain activation commands from top-level rb enable / rb exec to rb msvc enable / rb msvc exec, and renames the implementation from Devkit to Msvc, updating tests and documentation accordingly while keeping behavior the same.

Changes:

• Updated CLI dispatch and usage text to expose MSVC activation under the msvc subcommand.
• Renamed the implementation type from Devkit to Msvc and updated all test references.
• Updated README and design/test documentation to reflect the new command surface and terminology.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/rbmanager.Tests/Support/VsWhereScope.cs	Updates the test seam to override Msvc.VsWhere instead of Devkit.VsWhere.
tests/rbmanager.Tests/Support/Serial.cs	Updates serial-test documentation to reference Msvc.VsWhere.
tests/rbmanager.Tests/SmokeTests.cs	Updates internal API smoke assertions to reference Msvc.
tests/rbmanager.Tests/MsvcVsTests.cs	Renames VS-dependent tests and updates CLI invocation to rb msvc exec.
tests/rbmanager.Tests/MsvcHelperTests.cs	Renames helper tests and updates calls from Devkit to Msvc.
tests/rbmanager.Tests/MsvcActivationTests.cs	Renames activation tests and updates calls from Devkit to Msvc.
tests/rbmanager.Tests/CliE2eTests.cs	Updates E2E dispatch-usage test cases for the new msvc command surface.
src/rbmanager/Program.cs	Updates CLI argument dispatch and usage text to msvc enable/exec.
src/rbmanager/Msvc.cs	Renames implementation class and updates comments/docs pointers to MSVC terminology.
README.md	Updates the user-facing command list and docs link to msvc enable/exec.
docs/test-plan.md	Updates the command contract/test plan to reflect rb msvc enable/exec and Msvc seams.
docs/msvc-enable.md	Updates the design note and examples to the new rb msvc enable/exec command surface.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.