Add SwiftLint configuration and CI enforcement

[NachoSoto]

Summary

• add a shared SwiftLint configuration and instructions for contributors to run it locally
• keep the DiskCache force-try file operations but annotate them with targeted swiftlint:disable:next force_try comments so linting passes without changing runtime behavior
• extend the build-and-test workflow to install SwiftLint and run it with the GitHub Actions reporter after the test suite

Testing

• ./.tools/swiftlint --config .swiftlint.yml

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Codex Task