remove: all legacy file cleanup functionality

- Removed scanForLegacyFiles, performCleanup, and related methods from installer.js
- Removed --skip-cleanup option from install command
- Deleted cleanup.js command file entirely
- Simplified installation flow by removing cleanup prompts
- All tests passing after removal

tools/cli/commands/install.js

@@ -9,7 +9,7 @@ const ui = new UI();
 module.exports = {
   command: 'install',
   description: 'Install BMAD Core agents and tools',
-  options: [['--skip-cleanup', 'Skip automatic cleanup of legacy files']],
+  options: [],
   action: async (options) => {
     try {
       const config = await ui.promptInstall();
@@ -44,11 +44,6 @@ module.exports = {
         config._requestedReinstall = true;
       }
 
-      // Add skip cleanup flag if option provided
-      if (options && options.skipCleanup) {
-        config.skipCleanup = true;
-      }
-
       // Regular install/update flow
       const result = await installer.install(config);