Require ObservableScopes of state holders to be specified explicitly

Previously we had a ViewModel class which was responsible for little more than creating an ObservableScope. However, since this ObservableScope would be created implicitly upon view model construction, it became a tad bit harder for callers to remember to eventually end the scope (as you wouldn't just have to remember to end ObservableScopes, but also to destroy ViewModels). Requiring the scope to be specified explicitly by the caller also makes it possible for the caller to reuse the scope for other purposes, reducing the number of scopes mentally in flight that need tending to, and for all state holders (not just view models) to be handled uniformly by helper functions such as generateKeyed$.

src/room/InCallView.tsx

@@ -110,6 +110,7 @@ import ringtoneMp3 from "../sound/ringtone.mp3?url";
 import ringtoneOgg from "../sound/ringtone.ogg?url";
 import { useTrackProcessorObservable$ } from "../livekit/TrackProcessorContext.tsx";
 import { type Layout } from "../state/layout-types.ts";
+import { ObservableScope } from "../state/ObservableScope.ts";
 
 const maxTapDurationMs = 400;
 
@@ -129,8 +130,10 @@ export const ActiveCall: FC<ActiveCallProps> = (props) => {
 
   const trackProcessorState$ = useTrackProcessorObservable$();
   useEffect(() => {
-    const reactionsReader = new ReactionsReader(props.rtcSession);
+    const scope = new ObservableScope();
+    const reactionsReader = new ReactionsReader(scope, props.rtcSession);
     const vm = new CallViewModel(
+      scope,
       props.rtcSession,
       props.matrixRoom,
       mediaDevices,
@@ -146,11 +149,9 @@ export const ActiveCall: FC<ActiveCallProps> = (props) => {
     );
     setVm(vm);
 
-    const sub = vm.leave$.subscribe(props.onLeft);
+    vm.leave$.pipe(scope.bind()).subscribe(props.onLeft);
     return (): void => {
-      vm.destroy();
-      sub.unsubscribe();
-      reactionsReader.destroy();
+      scope.end();
     };
   }, [
     props.rtcSession,