Administration: Use SVG icons in the At a Glance dashboard widget

[elphizu]

Replace the Dashicons in the “At a Glance” dashboard widget with registered core SVG icons. Preserve warning colors, plugin-added icon fallbacks, and SVG icons when comment counts update via AJAX.

Trac ticket: https://core.trac.wordpress.org/ticket/66347

Screenshots

Testing

• PHP syntax and coding standards checks passed.
• JavaScript lint checks passed.
• CSS processing and RTL spacing checks passed.
• Verified AJAX count updates preserve both comment icons.

Use of AI Tools

AI assistance: Yes
Tool(s): OpenAI Codex
Used for: Icons lookup, PR Desciption, and replacing the icons.

[github-actions]

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[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

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Props suryakantupadhyay.

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