Address search PR review comments

- Drop the redundant searchService coordinator/view model parameter; derive it from the client proxy.
- Rename the globalSearch avatar size to search.
- Lift the query observation streams out of their tasks.
- Restore the appeared and updateVisibleRange comments.
- Use CompoundIcon defaults and a scaledFrame for media previews.
- Simplify the result mapping with compactMap(makeResult) and drop unsupported events by returning nil.
- Move the preview helpers beneath the previews.

ElementX/Sources/Screens/SearchScreen/SearchScreenViewModel.swift

@@ -25,14 +25,13 @@ class SearchScreenViewModel: SearchScreenViewModelType, SearchScreenViewModelPro
     }
     
     init(roomSummaryProvider: RoomSummaryProviderProtocol,
-         searchService: SearchServiceProxyProtocol,
          clientProxy: ClientProxyProtocol,
          mediaProvider: MediaProviderProtocol,
          initialSearchQuery: String = "",
          initialSearchMode: SearchScreenMode = .rooms) {
         self.roomSummaryProvider = roomSummaryProvider
-        self.searchService = searchService
         self.clientProxy = clientProxy
+        searchService = clientProxy.searchService
         
         super.init(initialViewState: SearchScreenViewState(bindings: .init(searchQuery: initialSearchQuery, searchMode: initialSearchMode)),
                    mediaProvider: mediaProvider)
@@ -68,18 +67,18 @@ class SearchScreenViewModel: SearchScreenViewModelType, SearchScreenViewModelPro
             }
             .store(in: &cancellables)
         
+        let debouncedSearchQueryStream = context.observe(\.viewState.bindings.searchQuery).debounce(for: .milliseconds(250)).removeDuplicates()
         searchQueryObservationTask = Task { [weak self] in
-            guard let stream = self?.context.observe(\.viewState.bindings.searchQuery).debounce(for: .milliseconds(250)).removeDuplicates() else { return }
-            for await searchQuery in stream {
+            for await searchQuery in debouncedSearchQueryStream {
                 self?.updateFilter(for: searchQuery)
             }
         }
         
         // Flip the loading indicator on the moment the user starts typing, ahead of the debounced
         // query above, so the empty state doesn't flash while the first search is still pending.
+        let searchQueryStream = context.observe(\.viewState.bindings.searchQuery).removeDuplicates()
         loadingObservationTask = Task { [weak self] in
-            guard let stream = self?.context.observe(\.viewState.bindings.searchQuery).removeDuplicates() else { return }
-            for await searchQuery in stream {
+            for await searchQuery in searchQueryStream {
                 self?.state.isLoadingRooms = !searchQuery.isEmpty
                 self?.state.isLoadingMessages = !searchQuery.isEmpty
             }
@@ -101,6 +100,8 @@ class SearchScreenViewModel: SearchScreenViewModelType, SearchScreenViewModelPro
         
         switch viewAction {
         case .appeared:
+            // The provider is shared, so other consumers may have changed its filter while we were off-screen.
+            // Re-apply ours on every appearance to keep the displayed results in sync with the query.
             updateFilter(for: state.bindings.searchQuery)
         case .selectRoom(let roomID):
             actionsSubject.send(.presentRoom(roomID: roomID, eventID: nil))
@@ -156,6 +157,12 @@ class SearchScreenViewModel: SearchScreenViewModelType, SearchScreenViewModelPro
         }
     }
     
+    /// The actual range values don't matter as long as they contain the lower
+    /// or upper bounds. updateVisibleRange is a hybrid API that powers both
+    /// sliding sync visible range update and list paginations.
+    /// For lists other than the home screen one we don't care about visible ranges,
+    /// we just need the respective bounds to be there to trigger a next page load or
+    /// a reset to just one page.
     private func updateVisibleRange(edge: UIRectEdge) {
         switch edge {
         case .top: