config: show Windows build on WSL

[MikeMcQuaid]

• read Edition, display version and build from registry
• expose the host Windows version in brew config
• fall back to ver when registry output is unavailable

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[Copilot]

Pull request overview

This PR extends brew config on Linux/WSL to expose the host Windows version/build, primarily by querying the Windows registry via cmd.exe (with a fallback to ver when registry data is unavailable).

Changes:

• Add a SystemConfig.windows_version API returning the host Windows version string on WSL.
• Implement Windows version detection on Linux/WSL using reg query (plus ver fallback) and print it in verbose config output.
• Add RSpec coverage for parsing/formatting the Windows version and for the additional brew config output line on WSL.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
Library/Homebrew/test/cmd/config_spec.rb	Adds tests for WSL Windows-version detection and for the new verbose config output line.
Library/Homebrew/system_config.rb	Introduces a windows_version method on SystemConfig (default nil).
Library/Homebrew/extend/os/linux/system_config.rb	Implements WSL Windows version detection (registry + ver fallback) and prints it in dump_verbose_config.

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