feat(plugin): Add Cosmetic Committee plugin for aesthetic UI customization

[thirdeyenation]

This PR introduces the "Cosmetic Committee", a fully functional Agent Zero plugin consisting of a multi-agent team dedicated to aesthetic customization of the Web UI.

Overview

Users can chat with the user-facing agent, cosmo, to request visual changes to the interface or apply one of 3 pre-built themes. Cosmo orchestrates the task by calling the lead_designer, who delegates to a css_specialist to write the code. Finally, a qa_specialist strictly reviews the CSS for destructive or unsafe properties (e.g., hiding critical UI elements or external imports) before applying the code using the new apply_css tool.

Technical Implementation

• Frontend Extension: Injects a reactive <style> tag into the page-head extension point.
• State Management: Introduces an Alpine.js cosmeticStore that fetches the active CSS payload via a new backend API endpoint on load and listens for cosmetic_css_update events over the WebSocket to apply changes live.
• Backend API: Adds /api/plugins/cosmetic_committee/get_css to serve the current theme.
• Tooling: Adds apply_css to save the CSS, broadcast the update to connected clients (mq.broadcast), and send a success toast notification (AgentNotification.success).

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PR created automatically by Jules for task 9239461664492628749 started by @thirdeyenation

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