A test pins attaching a look to an app: only `phone` or `desktop`, and only to a repository that is an app #7113

attachLook in src/actions/attach_look.ts refuses no_app and bad_width, and no test names bad_width.

Done:

• [ ] A new test attaches a phone look and a desktop look to an app, and both are kept.
• [ ] Width tablet, an empty string and a number are each bad_width. A repository that is not an app is no_app.
• [ ] After each refusal, nothing is stored.

Files: test/attach-look-refusals.test.ts

If the test finds the behaviour wrong, fix the action in the same pull and say so.

If the check fails in a test this pull does not touch, name it in the pull rather than widening the change.

Before pushing: bun x tsc --noEmit and the tests this names.