Show recent searches on the search screen

The search screen's empty state now lists the queries the user searched
for and the rooms they opened from the results, newest first, capped at 25
and stored in AppSettings. Tapping a query fills the search field, tapping
a room opens it, and both are reachable with a hardware keyboard.

Rooms are resolved from their identifiers as the room list loads, and
those the user has left or is only invited to are dropped. The history is
cleared on logout.

UnitTests/Sources/SearchScreenViewModelTests.swift

@@ -14,6 +14,9 @@ struct SearchScreenViewModelTests {
     let viewModel: SearchScreenViewModelProtocol
     let searchService: SearchServiceProxyMock
     let userIndicatorController: UserIndicatorControllerMock
+    let appSettings: AppSettings
+    /// The rooms known to the client, empty until the room list loads.
+    let staticRoomListSubject = CurrentValueSubject<[RoomSummary], Never>([])
     /// Fires with the query each time the (async, debounced) message search runs.
     let setQuerySubject = PassthroughSubject<String, Never>()
     /// Fires each time an indicator is submitted.
@@ -39,11 +42,20 @@ struct SearchScreenViewModelTests {
         
         let clientProxy = ClientProxyMock(.init())
         clientProxy.searchService = searchService
+        let staticRoomSummaryProvider = RoomSummaryProviderMock()
+        staticRoomSummaryProvider.roomListPublisher = staticRoomListSubject.asCurrentValuePublisher()
+        clientProxy.staticRoomSummaryProvider = staticRoomSummaryProvider
+        clientProxy.roomSummaryForIdentifierClosure = { [staticRoomListSubject] identifier in
+            staticRoomListSubject.value.first { $0.id == identifier }
+        }
+        
+        appSettings = AppSettings.volatile()
         
         viewModel = SearchScreenViewModel(roomSummaryProvider: RoomSummaryProviderMock(.init(state: .loaded(.mockRooms))),
                                           clientProxy: clientProxy,
                                           mediaProvider: MediaProviderMock(.init()),
-                                          userIndicatorController: userIndicatorController)
+                                          userIndicatorController: userIndicatorController,
+                                          appSettings: appSettings)
     }
     
     @Test
@@ -94,6 +106,47 @@ struct SearchScreenViewModelTests {
         try await deferred.fulfill()
     }
     
+    @Test
+    func selectionRecordsBreadcrumbs() {
+        context.searchQuery = "Second"
+        context.send(viewAction: .selectRoom(roomID: "2"))
+        
+        #expect(appSettings.searchBreadcrumbs == [.room(roomID: "2"), .query("Second")])
+        
+        // Selecting the same room again from the empty state only bumps it back to the top.
+        context.searchQuery = ""
+        context.send(viewAction: .selectRoom(roomID: "2"))
+        
+        #expect(appSettings.searchBreadcrumbs == [.room(roomID: "2"), .query("Second")])
+    }
+    
+    @Test
+    func breadcrumbsAreDisplayed() async throws {
+        staticRoomListSubject.send([.mock(id: "2", name: "Second")])
+        
+        let deferred = deferFulfillment(context.observe(\.viewState.breadcrumbs)) { $0.count == 2 }
+        appSettings.searchBreadcrumbs = [.query("Second"), .room(roomID: "2")]
+        try await deferred.fulfill()
+        
+        #expect(context.viewState.breadcrumbs.map(\.id) == ["query-Second", "room-2"])
+    }
+    
+    /// The room list is empty when the app launches, so the rooms need resolving again once it has loaded.
+    @Test
+    func roomBreadcrumbsAreDisplayedAfterTheRoomListLoads() async throws {
+        var deferred = deferFulfillment(context.observe(\.viewState.breadcrumbs)) { $0.count == 1 }
+        appSettings.searchBreadcrumbs = [.query("Second"), .room(roomID: "2")]
+        try await deferred.fulfill()
+        
+        #expect(context.viewState.breadcrumbs.map(\.id) == ["query-Second"])
+        
+        deferred = deferFulfillment(context.observe(\.viewState.breadcrumbs)) { $0.count == 2 }
+        staticRoomListSubject.send([.mock(id: "2", name: "Second")])
+        try await deferred.fulfill()
+        
+        #expect(context.viewState.breadcrumbs.map(\.id) == ["query-Second", "room-2"])
+    }
+    
     @Test
     func cancel() async throws {
         let deferred = deferFulfillment(viewModel.actionsPublisher) { action in