Add TemporaryMatrixClient interface

This is an abstraction over an actual unauthenticated `Client` from the SDK that implements `GetUrlResolver`, and is supposed to be short-lived.

With this, we can use the SDK network stack to perform arbitrary GET url operations.

The `AutoCloseable` implementation makes it easier to clean up any leftover local config after using this temporary client.

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/TemporaryMatrixClient.kt

@@ -0,0 +1,18 @@
+/*
+ * 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.api
+
+import java.lang.AutoCloseable
+
+/**
+ * A Matrix client in an 'unauthenticated' state that can still be used to resolve URLs.
+ *
+ * Note: this client implements an [AutoCloseable] interface, so using [AutoCloseable.close] or [AutoCloseable.use] will clean up any resources associated
+ * with it, such as temporary files.
+ */
+interface TemporaryMatrixClient : GetUrlResolver, AutoCloseable

libraries/matrix/api/src/main/kotlin/io/element/android/libraries/matrix/api/TemporaryMatrixClientFactory.kt

@@ -0,0 +1,15 @@
+/*
+ * 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.api
+
+/**
+ * Factory to create a temporary [TemporaryMatrixClient] for a given home server URL.
+ */
+interface TemporaryMatrixClientFactory {
+    suspend fun createTemporaryMatrixClient(homeServerUrl: String): Result<TemporaryMatrixClient>
+}

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/RustTemporaryMatrixClient.kt

@@ -0,0 +1,36 @@
+/*
+ * 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.impl
+
+import io.element.android.libraries.core.extensions.mapFailure
+import io.element.android.libraries.core.extensions.runCatchingExceptions
+import io.element.android.libraries.matrix.api.TemporaryMatrixClient
+import io.element.android.libraries.matrix.api.paths.SessionPaths
+import io.element.android.libraries.matrix.impl.exception.mapClientException
+import org.matrix.rustcomponents.sdk.Client
+
+class RustTemporaryMatrixClient(
+    private val client: Client,
+    private val paths: SessionPaths?,
+) : TemporaryMatrixClient {
+    override suspend fun getUrl(url: String): Result<ByteArray> = runCatchingExceptions {
+        client.getUrl(url)
+    }.mapFailure { it.mapClientException() }
+
+    override fun close() {
+        client.close()
+        paths?.let {
+            if (it.fileDirectory.exists()) {
+                it.fileDirectory.deleteRecursively()
+            }
+            if (it.cacheDirectory.exists()) {
+                it.cacheDirectory.deleteRecursively()
+            }
+        }
+    }
+}

libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/RustTemporaryMatrixClientFactory.kt

@@ -0,0 +1,36 @@
+/*
+ * 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.impl
+
+import dev.zacsweers.metro.AppScope
+import dev.zacsweers.metro.ContributesBinding
+import io.element.android.libraries.core.extensions.runCatchingExceptions
+import io.element.android.libraries.matrix.api.TemporaryMatrixClientFactory
+import io.element.android.libraries.matrix.api.TemporaryMatrixClient
+import io.element.android.libraries.matrix.impl.paths.SessionPathsFactory
+
+@ContributesBinding(AppScope::class)
+class RustTemporaryMatrixClientFactory(
+    private val sessionPathsFactory: SessionPathsFactory,
+    private val rustMatrixClientFactory: RustMatrixClientFactory,
+) : TemporaryMatrixClientFactory {
+    override suspend fun createTemporaryMatrixClient(homeServerUrl: String): Result<TemporaryMatrixClient> {
+        return runCatchingExceptions {
+            val sessionPaths = sessionPathsFactory.create()
+            val client = rustMatrixClientFactory.getBaseClientBuilder(
+                sessionPaths = sessionPaths,
+                clientSecret = null,
+                slidingSyncType = ClientBuilderSlidingSync.Native,
+                isMessageSearchAvailable = false,
+            )
+                .homeserverUrl(homeServerUrl)
+                .build()
+            RustTemporaryMatrixClient(client, sessionPaths)
+        }
+    }
+}