Avoid trust errors for cask conflicts

[MikeMcQuaid]

• conflicts_with casks may be uninstalled candidates from third-party taps.
• Loading those tap casks forces trust for packages the user did not request.
• Prefer installed metadata so real conflicts still fail without trusting candidates.

Fixes #23021

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[Copilot]

Pull request overview

This PR addresses trust enforcement failures when a cask’s conflicts_with references other casks from third-party taps, ensuring the user doesn’t need to trust uninstalled conflict candidates while still detecting real conflicts.

Changes:

• Prefer installed cask metadata when resolving conflicting casks to avoid loading tap casks unnecessarily.
• Ignore Homebrew::UntrustedTapError when evaluating conflicts so untrusted/uninstalled conflict candidates don’t block installs.
• Add a regression spec covering the untrusted/uninstalled conflicting cask scenario.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
Library/Homebrew/cask/installer.rb	Adjusts conflict resolution to prefer installed caskfiles and to ignore untrusted/unavailable conflict candidates.
Library/Homebrew/test/cask/dsl_spec.rb	Adds a test case ensuring untrusted, uninstalled conflicting casks do not raise during conflict checks.

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