Ask for session verification before sharing with an unverified account

The incoming share is now displayed on top of the root, so the FTUE, and the session verification in particular, could be bypassed.

- When the current account is not verified, wait for the FTUE to be complete before displaying the incoming share, as before.
- When the user selects another account which is not verified in the room select screen, display the session verification flow of
  the FTUE for this account on top of the share. As in the FTUE, the user has to verify the session or to sign out.
- Expose the FTUE session verification flow with a new SessionVerificationEntryPoint, displayed by OtherSessionVerificationNode
  which sets up the session graph of the account to verify.
- Introduce RoomSelectNavigator so that RoomSelectPresenter can request the verification of the selected session.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

features/ftue/api/src/main/kotlin/io/element/android/features/ftue/api/SessionVerificationEntryPoint.kt

@@ -0,0 +1,32 @@
+/*
+ * 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.features.ftue.api
+
+import com.bumble.appyx.core.modality.BuildContext
+import com.bumble.appyx.core.node.Node
+import com.bumble.appyx.core.plugin.Plugin
+import io.element.android.libraries.architecture.FeatureEntryPoint
+
+/**
+ * Entry point to the session verification flow displayed during the FTUE, to be used outside of the FTUE.
+ * As in the FTUE, the user cannot go back from this flow: they have to verify the session or to sign out.
+ */
+interface SessionVerificationEntryPoint : FeatureEntryPoint {
+    fun createNode(
+        parentNode: Node,
+        buildContext: BuildContext,
+        callback: Callback,
+    ): Node
+
+    interface Callback : Plugin {
+        /**
+         * Called when the session has been verified.
+         */
+        fun onDone()
+    }
+}