drush vale:lint passes a scope that Vale does not check

Problem/Motivation

drush vale:lint ENTITY_TYPE:BUNDLE prints an empty table and exits 0 when nothing in the bundle is checked by Vale. That reads as a clean pass. On a Drupal CMS site, vale:lint canvas_page:canvas_page does exactly that, so a CI step passes on content Vale never saw.

Steps to reproduce

1. Create a content type with no field opted in to Vale.
2. Run drush vale:lint node:that_type. It prints an empty table and exits 0.

Proposed resolution

• Refuse a scope with nothing checked by Vale: "No field in node:that_type is checked with Vale.", exit 1.
• Count a bundle as checked when it has an opted-in field, or when a component it can hold, such as a paragraph type, has one. Follow only references to component types, as linting does, and search each bundle once.
• Say so in the README.

Remaining tasks

• Review and merge.