Add a script to check stability of State classes

tom script

tools/compose/check_stability.sh

@@ -0,0 +1,23 @@
+#!/usr/bin/env bash
+
+# Copyright 2025 New Vector Ltd.
+#
+# SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+# Please see LICENSE files in the repository root for full details.
+
+set -e
+
+# Build the project with compose report
+echo "Building the project with compose report..."
+./gradlew assembleGplayDebug -PcomposeCompilerReports=true -PcomposeCompilerMetrics=true --stacktrace
+
+echo "Checking stability of State classes..."
+# Using the find command, list all the files ending with -classes.txt
+find . -type f -name "*-classes.txt" | while read -r file; do
+    # echo "Processing $file"
+    # Check that there is no line containing "unstable class .*State {"
+    if grep -E 'unstable class .*State \{' "$file"; then
+        echo "Found unstable State class in $file"
+        exit 1
+    fi
+done