Site Editor: Fix Template Parts post type preload path

[Mamaduka]

What?

PR fixes a typo in the Template Parts post-type preload path. This type has been around since the beginning—#36488.

Why?

Incorrect preload paths result in a silent WP error, and noting gets preloaded. I only noticed this because I was checking REST API responses and was curious where WP_Error originated.

Maybe rest_preload_api_request should log a _doing_it_wrong() when a provided path resolves with an error.

Testing Instructions

1. Navigate to site-editor.php?postType=wp_template_part.
2. The app shouldn't make a types/wp_template_part request. It does on the trunk.

Testing Instructions for Keyboard

Same.

Screenshots or screencast

[github-actions]

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Co-authored-by: Mamaduka <mamaduka@git.wordpress.org>
Co-authored-by: tyxla <tyxla@git.wordpress.org>

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[tyxla]

Wow, nice find @Mamaduka 💯

This fixes it, FWIW, so I'm approving 👍

I assume you preferred fixing it here instead of here so it gets fixed ASAP? I wonder if it should be fixed in core, though, and then once Gutenberg is merged into core, this filter would just be removed.

[Mamaduka]

Thanks for testing, @tyxla!

I think this is how we usually fix editor preload paths. Example #39256.

I'll create core PR separately for backport and a ticket to log _doing_it_wrong when the path resolves with an error, making it easier to catch similar bugs.

[tyxla]

Thought that might be it. Thanks for confirming and for fixing it @Mamaduka 🙌

[github-actions]

Flaky tests detected in 2bc08c2.
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/10347976331
📝 Reported issues:

• [Flaky Test] Navigates the items list via UP/DOWN arrow keys #64334 in /test/e2e/specs/site-editor/dataviews-list-layout-keyboard.spec.js