Show nerdfonts in Deepseek Harness web terminal using Tampermonkey script

nerdfonts.js

// Tampermonkey scriot: USE EXISTING HEADER, REMOVE THIS HEADER AND ONLY COPY THE CODE AFTER 'user strict'
// ==UserScript==
// @name         DeepSeek Local Nerd Font Canvas Enforcer
// @match        *://*:3080/*
// @run-at       document-start
// @grant        none
// ==UserScript==

(function() {
    'use strict';

    // 1. Target the raw HTML document element before any framework loops mount
    const style = document.createElement('style');
    style.innerHTML = `
        :root, html, body {
            --ds-font-family-code: "JetBrainsMono Nerd Font", "FiraCode Nerd Font", monospace !important;
            --dsw-font-code: "JetBrainsMono Nerd Font", "FiraCode Nerd Font", monospace !important;
            --dsw-font-monospace: "JetBrainsMono Nerd Font", "FiraCode Nerd Font", monospace !important;
        }
    `;
    document.documentElement.appendChild(style);

    // 2. Intercept dynamically built style nodes or shadow element injections
    const observer = new MutationObserver((mutations) => {
        mutations.forEach((mutation) => {
            mutation.addedNodes.forEach((node) => {
                if (node.nodeType === Node.ELEMENT_NODE) {
                    // Force the font family straight down into any component matching a terminal layout container
                    if (node.matches('div') || node.matches('canvas')) {
                        node.style.setProperty('font-family', '"JetBrainsMono Nerd Font", "FiraCode Nerd Font", monospace', 'important');
                    }
                    // Handle shadow-roots on components as they pop into view
                    if (node.shadowRoot) {
                        const shadowStyle = document.createElement('style');
                        shadowStyle.innerHTML = `* { font-family: "JetBrainsMono Nerd Font", "FiraCode Nerd Font", monospace !important; }`;
                        node.shadowRoot.appendChild(shadowStyle);
                    }
                }
            });
        });
    });

    observer.observe(document.documentElement, { childList: true, subtree: true });
})();