Constrain is-fullscreen-mode admin body class to posts list

[ntsekouras]

What?

Fixes a bug introduced here: #62705

This PR constrains the is-fullscreen-mode admin body class to posts list.

[github-actions]

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Co-authored-by: ntsekouras <[email protected]>
Co-authored-by: nerrad <[email protected]>

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[github-actions]

Flaky tests detected in ee2a4e3.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/9804072570
📝 Reported issues:

• [Flaky Test] submenu click on the arrow interactions #61884 in /test/e2e/specs/editor/blocks/navigation-frontend-interactivity.spec.js

[nerrad]

Code wise looks okay (with the caveat in my comment). I haven't tested so I'm assuming you've confirmed this still addresses the original reason the code was added.

[nerrad]

What confidence level is there that this route name will remain the same if/when this is ported to WordPress (given the gutenberg namespace used here). Should page references like this be returned from some sort of central map so that the name can be changed in one place when ported?

For example:

const PAGE_ROUTE_MAP = {
     POSTS_DASHBOARD: 'gutenberg-posts-dashboard',
     /** ...mapping for other known routes... **/
};

[ntsekouras]

This is just the v1 of posts lists that a GB experiment and we don't know when it's going to be added in core and will have many updates over time. Eventually it will have a specific admin page, where we won't have to do the redirection and these param checks, similar to the site editor page.

[nerrad]

Makes sense. Thanks for the fix!