restore xcode 26 and swift 6.2 defaults

[nickhart]

Summary

Accidentally reverted defaults to Xcode 16.0 and Swift 5.10. Restoring Xcode 26.0 and Swift 6.2 defaults.

Changes

• fixed setup.sh to use Xcode 26.0 and Swift 6.2

Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📚 Documentation update
• 🔧 Configuration change
• ♻️ Code refactoring
• 🧪 Test improvements
• 🔒 Security update

Testing

• Unit tests pass (./scripts/test.sh)
• UI tests pass (./scripts/test.sh --ui)
• Manual testing completed
• Code builds successfully (./scripts/build.sh)
• Linting passes (./scripts/lint.sh)
• Formatting is correct (./scripts/format.sh)

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published