Agent Skills: building-swift-apps

Builds, tests, and ships native Swift/SwiftUI apps for Apple platforms (macOS/iOS) reliably in CI and locally — unsigned CI builds, the hand-maintained pbxproj, SwiftPM-module vs app-target test boundaries, SourceKit false positives, gitignored base xcconfig, Keychain vs UserDefaults for secrets (OAuth state/PKCE), CloudKit/SwiftData constraints, and deterministic date/RNG handling. Use when wiring CI for an Xcode project, debugging "requires a provisioning profile" / "no testable scheme" / "cannot find type in scope", adding a Swift file to a target, wiring OAuth sign-in, or reviewing a Swift app.