[Tags] Disallow tag renaming with `Tab` key

### What
If tag is selected in the sidebar, `Tab` key should not start its editing. Users are still free to rename a tag with `return` key or with right-click.

### Why
After improvements targeted at `Tab` navigation, the currently existing behaviour of renaming a tag with `Tab` interferes with the expectation that `Tab` should move focus to the note list, if the sidebar was initially active.

Locate the sidebar tag selection, editing, and keyboard-focus handling in the macOS app, then trace how Tab differs from Return and right-click. Done means Tab moves focus to the note list when the sidebar is active, while Return and right-click still allow tag renaming.

Written by the indexing model from the issue text.