Add stderr test hook for UI experiment

src/hooks/stderr-test-hook.ts

@@ -0,0 +1,12 @@
+#!/usr/bin/env node
+
+/**
+ * Test hook to verify if stderr messages appear in Claude Code UI
+ * This hook simply outputs a message via console.error()
+ */
+
+// Output a test message to stderr
+console.error('🧪 TEST: This is a stderr message from the claude-mem hook');
+
+// Exit successfully
+process.exit(0);