/* ═══════════════════════════════════════════════════════════════
   SIDEBAR — OpenAI-style navigation
   ═══════════════════════════════════════════════════════════════ */

.sidebar-nav {
  position: fixed; top: 0; left: 0; width: var(--sidebar-width); height: 100vh;
  background: var(--bg-sidebar); border-right: 1px solid var(--border-subtle);
  display: flex; flex-direction: column; z-index: 200;
  transition: width var(--duration-slow) var(--ease-default);
}
.sidebar-nav.collapsed { width: var(--sidebar-collapsed); }

/* Header */
.sidebar-header {
  padding: var(--space-4) var(--space-4); border-bottom: 1px solid var(--border-subtle);
  display: flex; align-items: center; justify-content: space-between;
  min-height: var(--header-height); flex-shrink: 0;
}
.sidebar-brand { display: flex; align-items: center; gap: var(--space-3); overflow: hidden; }
.sidebar-brand-icon {
  width: 32px; height: 32px; display: flex; align-items: center; justify-content: center;
  font-size: var(--text-lg); color: var(--accent); flex-shrink: 0;
  background: var(--accent-muted); border-radius: var(--radius-md); font-weight: var(--weight-bold);
}
.sidebar-brand-text { display: flex; flex-direction: column; overflow: hidden; white-space: nowrap;
  transition: opacity var(--duration-normal); }
.sidebar-nav.collapsed .sidebar-brand-text { opacity: 0; width: 0; }
.sidebar-brand-name { font-size: var(--text-sm); font-weight: var(--weight-bold); color: var(--text-primary); }
.sidebar-user { font-size: var(--text-xs); color: var(--text-muted); margin-top: 1px; }

.sidebar-collapse-btn {
  width: 28px; height: 28px; border: none; background: transparent;
  color: var(--text-tertiary); cursor: pointer; border-radius: var(--radius-sm);
  display: flex; align-items: center; justify-content: center; font-size: var(--text-sm);
  transition: all var(--duration-fast); flex-shrink: 0;
}
.sidebar-collapse-btn:hover { background: var(--bg-hover); color: var(--text-primary); }
.sidebar-nav.collapsed .sidebar-collapse-btn .sidebar-collapse-icon { transform: rotate(180deg); }
.sidebar-collapse-icon { transition: transform var(--duration-normal); display: inline-block; }

/* Scrollable body */
.sidebar-body { flex: 1; overflow-y: auto; overflow-x: hidden; padding: var(--space-2) 0; }

/* Sections */
.nav-section { margin-bottom: var(--space-1); }
.nav-section-header {
  display: flex; align-items: center; gap: var(--space-2);
  padding: var(--space-2) var(--space-4) var(--space-1);
  cursor: pointer; user-select: none;
}
.nav-section-header:hover .nav-section-label { color: var(--text-tertiary); }
.nav-section-icon { font-size: var(--text-sm); flex-shrink: 0; width: 20px; text-align: center; }
.nav-section-label {
  font-size: 0.65rem; font-weight: var(--weight-bold); text-transform: uppercase;
  letter-spacing: 0.1em; color: var(--text-muted); white-space: nowrap;
  transition: opacity var(--duration-normal), color var(--duration-fast);
}
.sidebar-nav.collapsed .nav-section-label { opacity: 0; width: 0; }
.nav-section-chevron {
  margin-left: auto; font-size: 0.6rem; color: var(--text-muted);
  transition: transform var(--duration-normal), opacity var(--duration-normal);
}
.sidebar-nav.collapsed .nav-section-chevron { opacity: 0; }
.nav-section.collapsed .nav-section-chevron { transform: rotate(-90deg); }

/* Items */
.nav-section-items { overflow: hidden; transition: max-height var(--duration-slow) var(--ease-default); max-height: 500px; }
.nav-section.collapsed .nav-section-items { max-height: 0; }
.nav-item {
  display: flex; align-items: center; gap: var(--space-3);
  padding: var(--space-2) var(--space-4) var(--space-2) var(--space-5);
  cursor: pointer; color: var(--text-secondary); font-size: var(--text-sm);
  transition: all var(--duration-fast); white-space: nowrap; overflow: hidden;
  border-radius: 0; position: relative; margin: 0 var(--space-2);
  border-radius: var(--radius-md);
}
.nav-item:hover { background: var(--bg-hover); color: var(--text-primary); }
.nav-item.active {
  background: var(--accent-muted); color: var(--accent-text);
  font-weight: var(--weight-medium);
}
.nav-item-icon { font-size: var(--text-base); flex-shrink: 0; width: 20px; text-align: center; }
.nav-item-label { overflow: hidden; text-overflow: ellipsis; transition: opacity var(--duration-normal); }
.sidebar-nav.collapsed .nav-item-label { opacity: 0; width: 0; }
.nav-item-badge {
  margin-left: auto; font-size: 0.65rem; font-weight: var(--weight-semibold);
  padding: 1px 6px; border-radius: var(--radius-full);
  background: var(--accent-muted); color: var(--accent-text); flex-shrink: 0;
}
.sidebar-nav.collapsed .nav-item-badge { display: none; }

/* Footer */
.sidebar-footer { border-top: 1px solid var(--border-subtle); padding: var(--space-3) var(--space-3); flex-shrink: 0; }
.sidebar-logout-btn {
  display: flex; align-items: center; gap: var(--space-3); width: 100%;
  padding: var(--space-2) var(--space-3); border: none; background: transparent;
  color: var(--text-tertiary); cursor: pointer; font-size: var(--text-sm);
  border-radius: var(--radius-md); transition: all var(--duration-fast); font-family: var(--font-sans);
}
.sidebar-logout-btn:hover { background: var(--error-muted); color: var(--error); }
.sidebar-logout-icon { font-size: var(--text-md); }
.sidebar-nav.collapsed .sidebar-logout-label { opacity: 0; width: 0; overflow: hidden; }

/* Collapsed tooltips */
.sidebar-nav.collapsed .nav-item[title]::after {
  content: attr(title); position: absolute; left: 100%; top: 50%; transform: translateY(-50%);
  background: var(--bg-elevated); color: var(--text-primary); padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-sm); font-size: var(--text-xs); white-space: nowrap;
  box-shadow: var(--shadow-md); border: 1px solid var(--border-default);
  opacity: 0; pointer-events: none; transition: opacity var(--duration-fast);
  z-index: 300; margin-left: var(--space-2);
}
.sidebar-nav.collapsed .nav-item:hover[title]::after { opacity: 1; }

/* Layout push */
.app-layout { display: flex; min-height: 100vh; }
.app-main {
  flex: 1; margin-left: var(--sidebar-width); min-width: 0;
  transition: margin-left var(--duration-slow) var(--ease-default);
}
.sidebar-nav.collapsed ~ .app-main, body.sidebar-collapsed .app-main { margin-left: var(--sidebar-collapsed); }

/* Mobile */
.sidebar-overlay {
  display: none; position: fixed; inset: 0; background: rgba(0,0,0,0.5);
  z-index: 199; opacity: 0; transition: opacity var(--duration-slow);
}
.sidebar-overlay.visible { display: block; opacity: 1; }

@media (max-width: 768px) {
  .sidebar-nav { transform: translateX(-100%); width: 280px; box-shadow: var(--shadow-lg); }
  .sidebar-nav.mobile-open { transform: translateX(0); }
  .sidebar-nav.collapsed { width: 280px; transform: translateX(-100%); }
  .sidebar-nav.collapsed.mobile-open { transform: translateX(0); }
  .app-main { margin-left: 0 !important; }
  .mobile-menu-btn { display: flex !important; }
}

.mobile-menu-btn {
  display: none; width: 32px; height: 32px; border: none; background: transparent;
  color: var(--text-secondary); cursor: pointer; border-radius: var(--radius-sm);
  align-items: center; justify-content: center; font-size: 1.2rem;
}
.mobile-menu-btn:hover { background: var(--bg-hover); color: var(--text-primary); }
.nav-item.perm-hidden { display: none; }