hediet / vscode-observables

- Add DIContainer with parent/child hierarchy for service registration - Add inject() property transformer to inject services into ViewModels - Add createServiceKey<T>() for type-safe service keys - Add DIProvider and DIContext for React context integration - Update viewWithModel to auto-collect required contexts via OmitInjected type - Extract DI test components to di-test.tsx - Add Playwright tests for DI functionality