refactor: consolidate restore under backup command

mcpctl backup restore list/diff/to instead of separate mcpctl restore.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/cli/tests/completions.test.ts

@@ -119,7 +119,7 @@ describe('fish completions', () => {
   });
 
   it('non-project commands do not show with --project', () => {
-    const nonProjectCmds = ['status', 'login', 'logout', 'config', 'apply', 'backup', 'restore'];
+    const nonProjectCmds = ['status', 'login', 'logout', 'config', 'apply', 'backup'];
     const lines = fishFile.split('\n').filter((l) => l.startsWith('complete') && l.includes('-a '));
 
     for (const cmd of nonProjectCmds) {