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/e2e/cli-commands.test.ts

@@ -22,7 +22,6 @@ describe('CLI command registration (e2e)', () => {
     expect(commandNames).toContain('create');
     expect(commandNames).toContain('edit');
     expect(commandNames).toContain('backup');
-    expect(commandNames).toContain('restore');
   });
 
   it('old project and claude top-level commands are removed', () => {