feat: collapsible sidebar nav with localStorage state (#48)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LP9Q4kfCAYAjJnsbHBrViZ

panel/assets/css/nova.css

@@ -139,10 +139,21 @@ input[type="date"]::-webkit-calendar-picker-indicator { filter: invert(1) opacit
 
 .sidebar-section { padding: .75rem 0; }
 .sidebar-section-label {
+  display: flex; align-items: center; justify-content: space-between;
   font-size: .7rem; font-weight: 700; letter-spacing: .08em;
   text-transform: uppercase; color: var(--text-muted);
   padding: .25rem 1.25rem .5rem;
+  cursor: pointer; user-select: none;
+  transition: color .15s;
 }
+.sidebar-section-label:hover { color: var(--text); }
+.sidebar-section-label .nav-chevron {
+  font-style: normal; font-size: .65rem; opacity: .5;
+  transition: transform .2s ease;
+  flex-shrink: 0;
+}
+.sidebar-section.collapsed .nav-chevron { transform: rotate(-90deg); }
+.sidebar-section.collapsed .sidebar-link { display: none; }
 .sidebar-link {
   display: flex; align-items: center; gap: .75rem;
   padding: .55rem 1.25rem; text-decoration: none;

panel/public/assets/css/nova.css

@@ -139,10 +139,21 @@ input[type="date"]::-webkit-calendar-picker-indicator { filter: invert(1) opacit
 
 .sidebar-section { padding: .75rem 0; }
 .sidebar-section-label {
+  display: flex; align-items: center; justify-content: space-between;
   font-size: .7rem; font-weight: 700; letter-spacing: .08em;
   text-transform: uppercase; color: var(--text-muted);
   padding: .25rem 1.25rem .5rem;
+  cursor: pointer; user-select: none;
+  transition: color .15s;
 }
+.sidebar-section-label:hover { color: var(--text); }
+.sidebar-section-label .nav-chevron {
+  font-style: normal; font-size: .65rem; opacity: .5;
+  transition: transform .2s ease;
+  flex-shrink: 0;
+}
+.sidebar-section.collapsed .nav-chevron { transform: rotate(-90deg); }
+.sidebar-section.collapsed .sidebar-link { display: none; }
 .sidebar-link {
   display: flex; align-items: center; gap: .75rem;
   padding: .55rem 1.25rem; text-decoration: none;

panel/public/assets/js/nova.js

@@ -221,6 +221,40 @@ window.Nova = (() => {
   return { api, toast, modal, confirm, initNav, loadPage, progressBar, bytes, relTime, badge, serviceDot, escHtml, loading, loadingDone };
 })();
 
+// #48 Collapsible sidebar nav — shared across all panels
+document.addEventListener('DOMContentLoaded', () => {
+  const STORE = 'ncpx_nav_collapsed';
+  const state = JSON.parse(localStorage.getItem(STORE) || '{}');
+
+  document.querySelectorAll('.sidebar-section').forEach(section => {
+    const label = section.querySelector('.sidebar-section-label');
+    if (!label) return;
+
+    // Add chevron icon
+    const chevron = document.createElement('i');
+    chevron.className = 'nav-chevron';
+    chevron.textContent = '▼';
+    label.appendChild(chevron);
+
+    const key = label.textContent.replace('▼','').trim();
+
+    // Restore saved state — default Overview open, others open
+    if (state[key]) section.classList.add('collapsed');
+
+    // Keep active page's section always open
+    const hasActive = section.querySelector('.sidebar-link.active');
+    if (hasActive) section.classList.remove('collapsed');
+
+    label.addEventListener('click', () => {
+      // Don't collapse if it contains the active link
+      if (section.querySelector('.sidebar-link.active')) return;
+      section.classList.toggle('collapsed');
+      state[key] = section.classList.contains('collapsed');
+      localStorage.setItem(STORE, JSON.stringify(state));
+    });
+  });
+});
+
 // #26 Mobile sidebar toggle — shared across all panels
 document.addEventListener('DOMContentLoaded', () => {
   const toggle  = document.getElementById('sidebar-toggle');