feat(swift-diagnostics): implement Phase 2.2 Swift Client SDK
New package ByteLystDiagnostics with:
- Core types: DiagnosticsSession, TraceSpan, LogEntry, Breadcrumb
- DiagnosticsClient: actor-based singleton with polling
- BreadcrumbTrail: ring buffer (max 100) for timeline
- NetworkInterceptor: URLProtocol-based HTTP capture
- DeviceState: battery, memory, storage, network, thermal
- 20+ XCTest unit tests
Features:
- configure()/start()/stop() lifecycle
- trace() async span wrapper
- log() with breadcrumb integration
- breadcrumb() manual timeline markers
- ETag-based config polling
- 30-second batch flush
Platforms: iOS 15+, macOS 13+, watchOS 8+, tvOS 15+
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