feat: add left panal collapsible-expandable functionality

webapp/static/styles.css

@@ -243,6 +243,22 @@ body {
     border-left: 2px solid var(--border-color);
     padding-left: 15px;
     margin-top: 8px;
+    overflow: hidden;
+    transition: max-height 0.3s ease-in-out, opacity 0.2s ease-in-out;
+}
+
+/* Collapsed state - hide children by default */
+.item-children.collapsed {
+    max-height: 0;
+    opacity: 0;
+    margin-top: 0;
+    margin-bottom: 0;
+}
+
+/* Expanded state */
+.item-children.expanded {
+    max-height: 1000px; /* Large enough to accommodate content */
+    opacity: 1;
 }
 
 .process-item {
@@ -260,6 +276,59 @@ body {
     background-color: var(--border-color);
 }
 
+/* Item header container */
+.item-header {
+    display: flex;
+    align-items: center;
+    gap: 4px;
+}
+
+/* Toggle button styles */
+.toggle-btn {
+    background: none;
+    border: none;
+    color: var(--text-secondary);
+    cursor: pointer;
+    padding: 4px;
+    border-radius: 4px;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    width: 20px;
+    height: 20px;
+    transition: all 0.2s ease;
+    font-size: 10px;
+    line-height: 1;
+}
+
+.toggle-btn:hover {
+    background-color: var(--hover-color);
+    color: var(--text-primary);
+    transform: scale(1.1);
+}
+
+.toggle-btn:focus {
+    outline: 2px solid var(--accent-color);
+    outline-offset: 2px;
+}
+
+/* Toggle icon rotation */
+.toggle-icon {
+    transition: transform 0.2s ease;
+    display: inline-block;
+}
+
+.toggle-btn.expanded .toggle-icon {
+    transform: rotate(90deg);
+}
+
+/* Spacer for items without children */
+.toggle-spacer {
+    width: 20px;
+    height: 20px;
+    display: inline-block;
+}
+
 .clickable {
     cursor: pointer;
     transition: all 0.2s ease;

webapp/templates/_partials/left_panel.html

@@ -1,17 +1,26 @@
 {% macro render_item(item) %}
     <li class="process-item status-{{ item.status }}">
-        <span hx-get="/content/{{ item.id }}" hx-target="#right-panel" hx-swap="innerHTML" class="item-name clickable">
-            <span class="status-icon">
-                {% if item.status == 'completed' %}✅
-                {% elif item.status == 'in_progress' %}⏳
-                {% elif item.status == 'error' %}❌
-                {% else %}⏸️
-                {% endif %}
+        <div class="item-header">
+            {% if item.children %}
+                <button class="toggle-btn" onclick="toggleNode(this)" aria-label="Toggle children">
+                    <span class="toggle-icon">▶</span>
+                </button>
+            {% else %}
+                <span class="toggle-spacer"></span>
+            {% endif %}
+            <span hx-get="/content/{{ item.id }}" hx-target="#right-panel" hx-swap="innerHTML" class="item-name clickable">
+                <span class="status-icon">
+                    {% if item.status == 'completed' %}✅
+                    {% elif item.status == 'in_progress' %}⏳
+                    {% elif item.status == 'error' %}❌
+                    {% else %}⏸️
+                    {% endif %}
+                </span>
+                {{ item.name }}
             </span>
-            {{ item.name }}
-        </span>
+        </div>
         {% if item.children %}
-            <ul class="item-children">
+            <ul class="item-children collapsed">
                 {% for child in item.children %}
                     {{ render_item(child) }}
                 {% endfor %}

webapp/templates/index.html

@@ -183,6 +183,26 @@
             document.getElementById('analysis_date').value = dateString;
         }
 
+        // Toggle node functionality for collapsible tree
+        function toggleNode(button) {
+            const children = button.parentElement.parentElement.querySelector('.item-children');
+            if (children) {
+                const isExpanded = children.classList.contains('expanded');
+                
+                if (isExpanded) {
+                    // Collapse
+                    children.classList.remove('expanded');
+                    children.classList.add('collapsed');
+                    button.classList.remove('expanded');
+                } else {
+                    // Expand
+                    children.classList.remove('collapsed');
+                    children.classList.add('expanded');
+                    button.classList.add('expanded');
+                }
+            }
+        }
+
         // Initialize the page
         document.addEventListener('DOMContentLoaded', function() {
             setCurrentDate();