```javascript
class AgenticTimeline extends HTMLElement {
    constructor() {
        super();
        this.attachShadow({ mode: 'open' });
    }

    connectedCallback() {
        this.render();
    }

    render() {
        this.shadowRoot.innerHTML = `
            <style>
                :host {
                    display: block;
                    margin-top: 2rem;
                }
                
                .timeline-header {
                    display: flex;
                    align-items: center;
                    margin-bottom: 1rem;
                }
                
                .timeline-container {
                    position: relative;
                    padding-left: 1.5rem;
                    border-left: 2px solid #e5e7eb;
                }
                
                .timeline-item {
                    position: relative;
                    padding-bottom: 1.5rem;
                }
                
                .timeline-dot {
                    position: absolute;
                    left: -1.5rem;
                    top: 0;
                    width: 1rem;
                    height: 1rem;
                    border-radius: 50%;
                    background-color: #3b82f6;
                    transform: translateX(-50%);
                }
                
                .timeline-content {
                    padding: 0.75rem;
                    background-color: white;
                    border-radius: 0.375rem;
                    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
                }
                
                .timeline-time {
                    font-size: 0.75rem;
                    color: #6b7280;
                    margin-bottom: 0.25rem;
                }
                
                .timeline-title {
                    font-weight: 500;
                    margin-bottom: 0.25rem;
                }
                
                .timeline-desc {
                    font-size: 0.875rem;
                    color: #4b5563;
                }
                
                .tool-call {
                    margin-top: 0.5rem;
                    padding: 0.5rem;
                    background-color: #f9fafb;
                    border-radius: 0.25rem;
                    font-size: 0.75rem;
                }
                
                .human-review {
                    margin-top: 0.5rem;
                    padding: 0.5rem;
                    border-radius: 0.25rem;
                    font-size: 0.75rem;
                }
                
                .review-approved {
                    background-color: #d1fae5;
                    color: #065f46;
                }
                
                .review-pending {
                    background-color: #fef3c7;
                    color: #92400e;
                }
            </style>
            
            <div class="timeline-header">
                <h3 class="text-lg font-medium">Execution Timeline</h3>
            </div>
            
            <div class="timeline-container">
                <div class="timeline-item">
                    <div class="timeline-dot"></div>
                    <div class="timeline-content">
                        <div class="timeline-time">2 minutes ago</div>
                        <div class="timeline-title">Cell #3 Completed</div>
                        <div class="timeline-desc">Data visualization generated</div>
                        
                        <div class="human-review review-pending">
                            <div>🧍 Human Review Required</div>
                            <div class="mt-1">Status: Pending</div>
                        </div>
                        
                        <div class="tool-call">
                            <div>