/* ==========================================================================
   Sidebar Folder Tree & Navigation
   ========================================================================== */

.sidebar-header {
  padding: 1.25rem 1.25rem 0.85rem 1.25rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-bottom: 1px solid var(--border-hairline);
}

.sidebar-title-eyebrow {
  font-family: var(--font-mono);
  font-size: 0.65rem;
  text-transform: uppercase;
  letter-spacing: 0.15em;
  color: var(--text-muted);
  font-weight: 600;
}

.sidebar-nav {
  padding: 1rem 0.75rem;
  flex: 1;
}

/* Tree Navigation List */
.tree-root-list,
.tree-children-list {
  list-style: none;
  padding-left: 0;
  margin: 0;
}

.tree-children-list {
  padding-left: 1rem;
  display: none;
  position: relative;
}

.tree-children-list::before {
  content: "";
  position: absolute;
  top: 0.25rem;
  bottom: 0.5rem;
  left: 0.65rem;
  width: 1px;
  background: var(--border-hairline);
}

.tree-folder-item.is-open > .tree-children-list {
  display: block;
}

.tree-item {
  margin: 0.15rem 0;
}

.tree-folder-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-radius: 6px;
  transition: background 0.15s ease;
}

.tree-folder-header:hover {
  background: var(--bg-hover);
}

.tree-folder-toggle {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.45rem 0.65rem;
  width: 100%;
  background: transparent;
  border: none;
  color: var(--text-ink);
  font-family: var(--font-sans);
  font-size: 0.875rem;
  font-weight: 500;
  text-align: left;
  cursor: pointer;
  min-height: 38px;
}

/* Folder Chevron 90deg over 120ms */
.folder-chevron {
  transition: transform 120ms cubic-bezier(0.4, 0, 0.2, 1);
  color: var(--text-muted);
  flex-shrink: 0;
}

.tree-folder-item.is-open > .tree-folder-header .folder-chevron {
  transform: rotate(90deg);
  color: var(--color-accent);
}

.tree-folder-title {
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.tree-folder-link {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.4rem;
  color: var(--text-faint);
  text-decoration: none;
  opacity: 0;
  transition: opacity 0.15s ease;
}

.tree-folder-header:hover .tree-folder-link {
  opacity: 1;
}

/* Note Link in Tree */
.tree-note-link {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.45rem 0.75rem;
  color: var(--text-muted);
  text-decoration: none;
  font-size: 0.85rem;
  border-radius: 6px;
  position: relative;
  transition: all 0.15s ease;
  min-height: 36px;
}

.tree-note-link:hover {
  background: var(--bg-hover);
  color: var(--text-ink);
}

/* Active Note — Signature Ember Marker */
.tree-note-link.is-active {
  background: var(--color-accent-light);
  color: var(--color-accent);
  font-weight: 600;
}

.tree-note-link.is-active::before {
  content: "";
  position: absolute;
  left: 0;
  top: 6px;
  bottom: 6px;
  width: 2.5px;
  border-radius: 9999px;
  background: var(--color-accent);
}

.tree-icon {
  font-size: 0.9rem;
  flex-shrink: 0;
}

.tree-label {
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.sidebar-empty {
  padding: 2rem 1.25rem;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--text-muted);
  line-height: 1.5;
  text-align: center;
}