Add as-console-user command

[MikeMcQuaid]

• Support MDM/Munki/Jamf runs where the parent process is root but Homebrew must execute as the logged-in macOS console user.
• Keep the nested operation constrained to HOMEBREW_BREW_FILE so this helper cannot become a general-purpose root command launcher.
• Share macos_user.sh with installer scripts so no-user and package plist fallback behaviour cannot drift between install paths.
• Stage macos_user.sh for pkgbuild because preinstall needs the resolver before the Homebrew payload has been installed.

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[Copilot]

Pull request overview

Adds a new brew as-console-user command and shared macOS user-resolution helper to support MDM/Munki/Jamf workflows where the parent process is root but Homebrew operations should run as the logged-in console user. Also refactors the macOS installer package scripts to share the same console-user and home-directory resolution logic, and stages that helper into the pkgbuild scripts bundle.

Changes:

• Add brew as-console-user (Ruby command definition + shell implementation) to re-dispatch a Homebrew command as the active macOS console user.
• Introduce Library/Homebrew/utils/macos_user.sh and update installer preinstall/postinstall scripts to use it for user/home resolution.
• Update the release workflow to stage macos_user.sh alongside installer scripts for pkgbuild.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
package/scripts/preinstall	Sources shared macOS user helper and validates a resolvable install user.
package/scripts/postinstall	Uses shared helper to select install user and resolve home directory for cache placement.
Library/Homebrew/utils/macos_user.sh	New standalone helper for console user, home directory, and package-user override logic.
Library/Homebrew/test/cmd/as-console-user_spec.rb	Adds unit tests for shell dispatch and user-resolution helper behavior.
Library/Homebrew/cmd/as-console-user.sh	Implements the shell-side homebrew-as-console-user dispatcher.
Library/Homebrew/cmd/as-console-user.rb	Declares the new command and its CLI docs/arg parsing.
Library/Homebrew/brew.sh	Exempts as-console-user from the “don’t run as root” guard.
.github/workflows/release.yml	Stages installer scripts + macos_user.sh for pkgbuild packaging.

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