Preserve GitHub token during eval

[MikeMcQuaid]

Fixes #22430

• Keep $HOMEBREW_GITHUB_API_TOKEN available while formulae and casks are evaluated so private taps can keep resolving assets.
• Share the eval scrubbing policy through ENV so formula and cask loaders do not drift.
• Add temporary HOMEBREW_NO_EVAL_ENV_SCRUBBING for users who need a short-term escape hatch while private taps migrate.

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[Copilot]

Pull request overview

This PR adjusts Homebrew’s “sensitive env scrubbing” during formula/cask evaluation to avoid breaking private-tap workflows that rely on HOMEBREW_GITHUB_API_TOKEN at load time, while keeping scrubbing in place for other sensitive variables by default.

Changes:

• Introduce an eval-specific env scrubbing helper that preserves HOMEBREW_GITHUB_API_TOKEN, and wire formula + cask loaders to use it.
• Add HOMEBREW_NO_EVAL_ENV_SCRUBBING as a temporary opt-out to disable eval-time scrubbing entirely.
• Add/extend unit tests and update Sorbet RBI for the new EnvConfig boolean.

Reviewed changes

Copilot reviewed 7 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
Library/Homebrew/test/formulary_spec.rb	Adds coverage for GitHub token preservation and the opt-out during formula evaluation.
Library/Homebrew/test/ENV_spec.rb	Adds coverage for clear_sensitive_environment! exceptions support.
Library/Homebrew/test/cask/cask_loader_spec.rb	Adds coverage for GitHub token preservation and the opt-out during cask evaluation.
Library/Homebrew/sorbet/rbi/dsl/homebrew/env_config.rbi	Adds RBI for no_eval_env_scrubbing?.
Library/Homebrew/formulary.rb	Switches formula evaluation to the eval-specific env scrubbing helper.
Library/Homebrew/extend/ENV/sensitive.rb	Adds exception support and eval-specific scrubbing behavior (incl. token allowlist + opt-out).
Library/Homebrew/env_config.rb	Adds HOMEBREW_NO_EVAL_ENV_SCRUBBING EnvConfig entry.
Library/Homebrew/cask/cask_loader.rb	Switches cask evaluation to the eval-specific env scrubbing helper.

Files not reviewed (1)

• Library/Homebrew/sorbet/rbi/dsl/homebrew/env_config.rbi: Language not supported

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