[Epic 1] Foundations: monorepo, build pipeline, design system & CI

[aquitaine]

Epic: Foundations

Stand up the project skeleton so every other epic can build, test, and ship safely.

Milestone: M0 · PRD: NFR-010, NFR-011, NFR-013, OSS-02

Scope

• SPM monorepo per PRD §18.3 (cross-platform packages + macOS target stubs).
• Platform-independent domain packages with swift test (DisplayDomain, ProviderInterfaces, SceneEngine, AutomationSchema, TopologyCore, SimulatorProvider).
• CI: cross-platform domain tests on Linux + macOS; SwiftLint.
• Xcode project/workspace wiring the macOS app, providers, rescue, CLI, and design system.
• OpenDisplayDesignSystem SwiftUI package: tokens + 14 components with #Previews (port from Packages/OpenDisplayDesignSystem/reference/).
• Public-API-only build scheme; enable the app-macos CI job (NFR-010).
• swift-format/SwiftLint enforced in CI.

Acceptance

• swift test green on Linux + macOS; xcodebuild builds full and public-API-only flavors; design-system previews render in Xcode.

Status

Scaffolding, domain packages, tests, CI, docs, and governance landed in the initial PR. Remaining items require Xcode on a Mac.