Add per-tool ignoreArchCheck field to Tool

[albertodebortoli]

Pull Request Title

Add per-tool ignoreArchCheck field to Tool

Description

• Adds an optional ignoreArchCheck: Bool? property to Tool, allowing each tool in the Lucafile to override the global --ignore-arch-check CLI flag.
• Precedence: per-tool true always skips arch validation; per-tool false always runs it; nil (field absent from YAML) falls back to the CLI flag.
• No breaking changes to the YAML format — the field is optional and existing Lucafiles continue to work unchanged.

Type of Change

• Feature

How Has This Been Tested?

• Added / updated unit tests
• Manually tested locally (describe)
• Tested on macOS (arch: arm64)

Four new installer tests cover all precedence scenarios:

• test_install_perToolIgnoreArchCheck_true_overridesGlobalFalse — per-tool true beats global false
• test_install_perToolIgnoreArchCheck_false_overridesGlobalTrue — per-tool false beats global true
• test_install_perToolIgnoreArchCheck_nil_fallsBackToGlobal_skips — nil + global true → no throw
• test_install_perToolIgnoreArchCheck_nil_fallsBackToGlobal_validates — nil + global false → throws

swift build   # ✅ clean
swift test    # ✅ 164 tests passed

Checklist

• Swift code builds locally (swift build)
• Tests pass locally (swift test)
• Code style / formatting respected
• Documentation updated (README / comments)

Breaking Changes?

• No

Additional Notes

Three new fixture files were added under Tests/Fixtures/Lucafiles/ for the per-tool tests. No Package.swift changes needed — the Fixtures directory is already registered as a resource.