Function useRuntimeManager

useRuntimeManager(
    initialRuntime?: RuntimeJSON,
): {
    selectedRuntime: RuntimeJSON;
    selectRuntime: (runtime: RuntimeJSON) => void;
    serviceManager: IManager;
}
Hook to manage runtime selection and service manager lifecycle.

Uses MutableServiceManager to maintain a stable serviceManager reference, preventing Notebook2 from re-rendering when runtimes are switched. This is crucial for UX - prevents cell flickering and scroll position loss.
Parameters
- OptionalinitialRuntime: RuntimeJSON
  Optional initial runtime to use
Returns {
    selectedRuntime: RuntimeJSON;
    selectRuntime: (runtime: RuntimeJSON) => void;
    serviceManager: IManager;
}
Runtime state and selection function
- selectedRuntime: RuntimeJSON
- selectRuntime: (runtime: RuntimeJSON) => void
  Select a runtime and update the underlying service manager. The MutableServiceManager reference stays stable - no component re-renders!
- serviceManager: IManager
Example
```
const { selectedRuntime, serviceManager, selectRuntime } = useRuntimeManager();

// Select a runtime
selectRuntime(runtime);

// Clear runtime (switch to mock)
selectRuntime(undefined);

// serviceManager reference stays stable - no Notebook2 re-render!
```
- Defined in webview/hooks/useRuntimeManager.ts:41