[ArkaPrabhaChowdhury]

The admin menu and admin bar depend on the non-public core-admin icon collection. Unregistering that collection, or one of its icons, currently leaves the corresponding admin UI without icons.

Reject those operations with _doing_it_wrong() and return false before changing either registry. The guards live in the registry methods so both direct calls and the public helpers are covered. Only core-admin is protected: the public core collection and third-party collections remain removable, including cascading removal of their icons.

Regression tests exercise both blocked operations, unchanged SVG output, and successful removal of core icons and their collection. The REST icon test fixture now uses temporary registry instances instead of unregistering the protected collection, and restores the original instances afterward.

Human verification

On a development installation with WP_DEBUG and WP_DEBUG_LOG enabled, add this temporary MU plugin:

<?php
add_action( 'init', function () {
    wp_unregister_icon_collection( 'core-admin' );
    wp_unregister_icon( 'core-admin/dashboard' );
}, 20 );

1. Open the dashboard. The admin menu and admin bar icons should remain visible. The debug log should contain an incorrect-usage notice for each attempted removal. Without the patch, the admin icons disappear.
2. Test each removal separately. Each call should return false, and wp_get_icon( 'core-admin/dashboard' ) should still return SVG markup.
3. Change the callback to unregister core/plus, then core. Both calls should return true; the public collection should be removed while the admin icons remain visible.
4. Remove the temporary MU plugin.

These are verification steps for a human reviewer; no completed human review is claimed.

Trac ticket: https://core.trac.wordpress.org/ticket/66344

Use of AI Tools

AI assistance: Yes
Tool(s): OpenAI Codex
Model(s): GPT-6
Used for: Ticket analysis, implementation, regression tests, local verification, and PR text. Human review remains pending.

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This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.

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