Rename stderr-test-hook to user-message-hook for production

Changes:
- Renamed src/hooks/stderr-test-hook.ts to user-message-hook.ts
- Updated user-message-hook with production-ready messaging
- Updated scripts/build-hooks.js to build user-message-hook
- Updated plugin/hooks/hooks.json to reference user-message-hook.js
- Cleaned up old stderr-test-hook.js files
- Built and deployed user-message-hook.js to plugin directory

This hook displays context information to users via stderr, which is
currently the only way to show messages in Claude Code UI. It runs in
parallel with context-hook during SessionStart.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/hooks/user-message-hook.ts

@@ -0,0 +1,26 @@
+/**
+ * User Message Hook - SessionStart
+ * Displays context information to the user via stderr
+ *
+ * This hook runs in parallel with context-hook to show users what context
+ * has been loaded into their session. Uses stderr as the communication channel
+ * since it's currently the only way to display messages in Claude Code UI.
+ */
+import { execSync } from "child_process";
+
+try {
+  const output = execSync("node ~/.claude/plugins/marketplaces/thedotmack/plugin/scripts/context-hook.js --colors", {
+    encoding: 'utf8'
+  });
+
+  console.error(
+    "\n\n📝 Claude-Mem Context Loaded\n" +
+    "   ℹ️  Note: This appears as stderr but is informational only\n\n" +
+    output
+  );
+
+} catch (error) {
+  console.error(`❌ Failed to load context display: ${error}`);
+}
+
+process.exit(3);