Feature: add room threads list (#6575)

Add threads list screen for rooms:

- Add `ThreadsListService` to subscribe to thread changes in the room.
- Create `ThreadsListView` and its associated node a presenters (the UI may change).
- Add a menu icon in the room screen to open it.

This is still pending info about unread threads, so several UI components related to it will be hidden.

* Add feature flag and use it to hide the access to this new screen

---------

Co-authored-by: ElementBot <android@element.io>

libraries/matrix/test/src/main/kotlin/io/element/android/libraries/matrix/test/room/FakeJoinedRoom.kt

@@ -35,6 +35,7 @@ import io.element.android.libraries.matrix.api.timeline.Timeline
 import io.element.android.libraries.matrix.api.widget.MatrixWidgetDriver
 import io.element.android.libraries.matrix.api.widget.MatrixWidgetSettings
 import io.element.android.libraries.matrix.test.notificationsettings.FakeNotificationSettingsService
+import io.element.android.libraries.matrix.test.room.threads.FakeThreadsListService
 import io.element.android.libraries.matrix.test.timeline.FakeTimeline
 import io.element.android.tests.testutils.lambda.lambdaError
 import io.element.android.tests.testutils.simulateLongTask
@@ -56,6 +57,7 @@ class FakeJoinedRoom(
     override val roomNotificationSettingsStateFlow: StateFlow<RoomNotificationSettingsState> =
         MutableStateFlow(RoomNotificationSettingsState.Unknown),
     override val knockRequestsFlow: Flow<List<KnockRequest>> = MutableStateFlow(emptyList()),
+    override val threadsListService: FakeThreadsListService = FakeThreadsListService(),
     private val roomNotificationSettingsService: FakeNotificationSettingsService = FakeNotificationSettingsService(),
     private var createTimelineResult: (CreateTimelineParams) -> Result<Timeline> = { lambdaError() },
     private val editMessageLambda: (EventId, String, String?, List<IntentionalMention>) -> Result<Unit> = { _, _, _, _ -> lambdaError() },

libraries/matrix/test/src/main/kotlin/io/element/android/libraries/matrix/test/room/threads/FakeThreadsListService.kt

@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial.
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+package io.element.android.libraries.matrix.test.room.threads
+
+import io.element.android.libraries.matrix.api.room.threads.ThreadListItem
+import io.element.android.libraries.matrix.api.room.threads.ThreadListPaginationStatus
+import io.element.android.libraries.matrix.api.room.threads.ThreadsListService
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.MutableStateFlow
+
+class FakeThreadsListService(
+    private val items: MutableStateFlow<List<ThreadListItem>> = MutableStateFlow(emptyList()),
+    private val paginationStatus: MutableStateFlow<ThreadListPaginationStatus> = MutableStateFlow(ThreadListPaginationStatus.Idle(hasMoreToLoad = true)),
+    private val subscribeToItemUpdates: () -> Flow<List<ThreadListItem>> = { items },
+    private val subscribeToPaginationUpdates: () -> Flow<ThreadListPaginationStatus> = { paginationStatus },
+    private val paginate: suspend () -> Result<Unit> = { Result.success(Unit) },
+    private val reset: suspend () -> Result<Unit> = { Result.success(Unit) },
+    private val destroy: () -> Unit = {},
+) : ThreadsListService {
+    override fun subscribeToItemUpdates(): Flow<List<ThreadListItem>> {
+        return subscribeToItemUpdates.invoke()
+    }
+
+    override fun subscribeToPaginationUpdates(): Flow<ThreadListPaginationStatus> {
+        return subscribeToPaginationUpdates.invoke()
+    }
+
+    override suspend fun paginate(): Result<Unit> {
+        return paginate.invoke()
+    }
+
+    override suspend fun reset(): Result<Unit> {
+        return reset.invoke()
+    }
+
+    override fun destroy() {
+        return destroy.invoke()
+    }
+
+    suspend fun emit(items: List<ThreadListItem>) {
+        this.items.emit(items)
+    }
+}