Deprecate the standalone sc-lint-boundary Homebrew formula #153

Problem

The sc-lint formula already installs the sc-lint-boundary executable. Maintaining and advertising a separate sc-lint-boundary formula is redundant and confusing.

Scope

Remove the legacy Homebrew formula without removing the sc-lint-boundary executable or its Rust crate.

Acceptance criteria

• Identify the canonical formula source/template and release automation that emits sc-lint-boundary.rb.
• Stop generating and publishing the standalone sc-lint-boundary formula.
• Remove the obsolete formula from randlee/homebrew-tap in a coordinated follow-up.
• Update installation/docs references to recommend brew install randlee/tap/sc-lint.
• Retain sc-lint-boundary as an executable installed by the sc-lint formula.
• Add a regression check that the generated sc-lint formula installs sc-lint-boundary and no separate legacy formula is emitted.

Migration

Existing users should install randlee/tap/sc-lint before removing the legacy formula. Do not attempt to silently uninstall the old formula.