The `global` `AssetLibrary` should not be loaded on all pages — only on routes where the negotiated theme is the default theme

wim leers → credited mglaman → .

Reported by @mglaman in chat.

This can break the admin theme! 😅🙈

I bet this fails because

    // Case 3: Route with _xb_use_template_draft should use regular asset
    // library if there is no auto-saved version.
    $assert_library_global_library('/xb/api/v0/layout/xb_page/' . $page->id(), TRUE);

does not negotiate the default theme.

Simpler than that:

• \Drupal\Core\Theme\ThemeManagerInterface::getActiveTheme returns a ActiveTheme object, not the theme name.
• The css selectors need to "contains" and not "startWith" because a) the subdir might be included if installed in subdirectory; b) 🐛 Provide cache buster query string on imports Active

Whoops — pretty evident now that I just threw up an MR without actually testing it! 😇

#9: RE: subdir — how come this worked fine until now?! 😳

#10 I haven't seen them fail nor tested it, but I was pretty sure this could be a problem?

Investigating the sole lingering concern: https://git.drupalcode.org/project/experience_builder/-/merge_requests/1...

Reverting those test changes passed just fine after locally I was convinced they were not needed — yay, zero concerns left! 🥳