Add Client-Side Navigation documentation to manifest and table of contents

[juanmaguitar]

What?

Follow up to #75263

Add the Client-Side Navigation documentation page to the docs manifest and table of contents so it appears in the developer documentation site.

Why?

PR #75263 added the client-side-navigation.md guide under Interactivity API Core Concepts, but the file was not registered in docs/manifest.json or docs/toc.json.
Without these entries, the page won't appear in the documentation site's navigation or be discoverable by readers.

How?

• Added an entry in docs/manifest.json for the client-side-navigation page under the core-concepts parent.
• Added an entry in docs/toc.json placing it after "Server-side rendering" and before "Using TypeScript", matching the order in the Core Concepts README.

Testing Instructions

Once merged, the Client Side Navigation guide should be available at https://developer.wordpress.org/block-editor/reference-guides/interactivity-api/core-concepts/client-side-navigation/

Note: Final documentation in the Block Editor Handbook is automatically regenerated from Gutenberg repo .md files every 15 minutes.

[github-actions]

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[github-actions]

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Co-authored-by: juanmaguitar <juanmaguitar@git.wordpress.org>
Co-authored-by: luisherranz <luisherranz@git.wordpress.org>

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[luisherranz]

LGTM!