brew search --desc: show casks without descriptions

[MikeMcQuaid]

• Keep cask name matches visible with the existing placeholder
• Preserve direct brew desc output for missing descriptions
• Handle incomplete cached cask description pairs safely

Fixes #23227

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OpenAI Codex GPT 5.6 Sol xhigh with local review and testing.

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[Copilot]

Pull request overview

This pull request addresses inconsistent brew search --desc results by ensuring casks that match by name are still shown even when they have no description, using a [no description] placeholder.

Changes:

• Update Descriptions#print to print cask entries with missing descriptions using a [no description] placeholder instead of skipping them.
• Add/adjust RSpec coverage to assert casks without descriptions are still emitted in search_descriptions output.

Reviewed changes

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

File	Description
Library/Homebrew/descriptions.rb	Print a placeholder for cask entries whose description is nil instead of skipping them.
Library/Homebrew/test/descriptions_spec.rb	Update expectation to require printing casks with missing descriptions.
Library/Homebrew/test/search_spec.rb	Add coverage for search_descriptions showing casks with no description when matched by name.

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