### cat\src\builder.js

```javascript
/**
 * Builder Module
 * 
 * This module takes the interpreted component parts and assembles them into a Custom Element class.
 */

class Builder {
    /**
     * Build a Custom Element class from the interpreted component parts with optimization:
     * - Build DOM once using a static DocumentFragment.
     * - Initialize variables in the constructor.
     * - Clone and append the fragment in connectedCallback.
     * 
     * @param {Object} component - The interpreted component object.
     * @param {string} component.tagName - The tag name for the custom element.
     * @param {Object} component.script - The interpreted script object.
     * @param {string[]} component.script.variables - Array of variable declarations.
     * @param {string[]} component.script.methods - Array of method definitions.
     * @param {string[]} component.script.calls - Array of function calls.
     * @param {Object} component.script.eventListeners - Object containing event listener registrations.
     * @param {string[]} component.script.eventListeners.connect - Array of event listener initialization statements.
     * @param {string[]} component.script.eventListeners.disconnect - Array of event listener removal statements.
     * @param {string} transformedDOM - The JavaScript code for building the DOM structure.
     * @returns {string} - The assembled Custom Element class as a string.
     */
    static buildCustomElement(component, transformedDOM) {
        const { tagName, script } = component;
        const className = this.kebabToPascalCase(tagName);

        // Initialize variables in the constructor
        const variableAssignments = script.variables.join('\n        ');

        // Event listeners for connect and disconnect
        const connectListeners = script.eventListeners.connect.join('\n        ');
        const disconnectListeners = script.eventListeners.disconnect.join('\n        ');

        // Function calls to execute after DOM is appended
        const functionCalls = script.calls.join('\n        ');

        // Methods of the class
        const methods = script.methods.join('\n\n    ');

        return `
class ${className} extends HTMLElement {
    /**
     * Static DocumentFragment shared across all instances.
     * Built once to optimize memory usage.
     */
    static _masterFragment = (function() {
        const fragment = document.createDocumentFragment();
        // Build the DOM once
        ${transformedDOM}
        return fragment;
    })();

    /**
     * Constructor initializes properties.
     */
    constructor() {
        super();
        // Initialize properties
        ${variableAssignments}
    }

    /**
     * Invoked each time the custom element is appended into a document-connected element.
     */
    connectedCallback() {
        // Clone the master fragment and append to the DOM
        const clonedFragment = ${className}._masterFragment.cloneNode(true);
        this.appendChild(clonedFragment);

        // Initialize event listeners
        ${connectListeners}

        // Execute any additional function calls
        ${functionCalls}
    }

    /**
     * Invoked each time the custom element is disconnected from the document's DOM.
     */
    disconnectedCallback() {
        // Remove event listeners
        ${disconnectListeners}
    }

    ${methods}
}

customElements.define('${tagName}', ${className});
        `.trim();
    }

    /**
     * Convert a kebab-case string to PascalCase.
     * 
     * @param {string} str - The kebab-case string to convert.
     * @returns {string} - The PascalCase version of the input string.
     */
    static kebabToPascalCase(str) {
        return str.split('-').map(part => part.charAt(0).toUpperCase() + part.slice(1)).join('');
    }
}

module.exports = Builder;
```

There's an issue in the way our connected callback it's appending our dom from the fragmented document. Can you evaluate it and find a solution, following our principle of single initialization, one single memory allocation for the fragmented document, not templates.