fix(core): fix lint/type issues and small refactors

ts/cli.ts

@@ -1,7 +1,7 @@
 import { execSync } from 'node:child_process';
 import { Nupst } from './nupst.ts';
 import { type ITableColumn, logger } from './logger.ts';
-import { symbols, theme } from './colors.ts';
+import { theme } from './colors.ts';
 
 /**
  * Class for handling CLI commands