bottle_specification: throw exception instead of panicking to be able to catch it

[botantony]

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[Copilot]

Pull request overview

This PR addresses issue #21582 by detecting legacy bottle sha256 DSL usage and preventing it from aborting formula auditing when walking historical revisions.

Changes:

• Add a new LegacyDSLError exception type to represent legacy DSL usage.
• Detect the legacy bottle sha256 hash-rocket form in BottleSpecification#sha256 and raise LegacyDSLError.
• Update FormulaAuditor#committed_version_info to rescue LegacyDSLError while traversing historical formula revisions.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 5 comments.

File	Description
Library/Homebrew/formula_auditor.rb	Rescues LegacyDSLError during committed-version history traversal.
Library/Homebrew/exceptions.rb	Introduces LegacyDSLError exception class.
Library/Homebrew/bottle_specification.rb	Expands sha256 signature and raises LegacyDSLError on legacy DSL usage.

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[MikeMcQuaid]

Looks good once comment addressed, thanks @botantony!

Before merging: please improve both the commit message and PR title/body so it's more apparent what's being done and why.