Feat v0.4.6 sidebar restructure

Restructure the notes sidebar with a two-tab header (Notes / Outline)
and relocate the document outline from the editor-side panel into the
sidebar's Outline tab with active heading tracking.

- Add SidebarTabs component with Notes/Outline tabs; Outline disabled
  when no note is selected
- Add SidebarOutline component with nested heading hierarchy
  (H1→H2→H3), depth indentation, and click-to-scroll
- Add RAF-throttled scroll listener for active heading highlighting
  based on scroll position (preview getBoundingClientRect / CM6 viewport)
- Lift headings, scrollToHeading, and activeHeadingIdx state to NotesApp
  via EditorPane callback props
- Remove old DocumentOutline component and .doc-outline CSS
- Auto-reset to Notes tab when active note is deleted
- Bump notes package to v0.7.0

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

packages/notes/css/main.css

@@ -632,57 +632,79 @@
   font-size: 11px;
 }
 
-/* ── Document Outline ─────────────────────── */
-.doc-outline {
-  width: 200px;
-  min-width: 160px;
-  border-left: 1px solid var(--border);
-  background: var(--bg-raised);
-  overflow-y: auto;
+/* ── Sidebar Tabs ────────────────────────── */
+.sidebar-tabs {
+  display: flex;
+  border-bottom: 1px solid var(--border);
   flex-shrink: 0;
 }
-.doc-outline__header {
-  font-size: 11px;
-  font-weight: 600;
+.sidebar-tabs__tab {
+  flex: 1;
+  padding: 10px 14px;
+  font-size: 13px;
+  font-weight: 500;
   color: var(--text-2);
-  text-transform: uppercase;
-  letter-spacing: 0.5px;
-  padding: 8px 10px;
-  display: flex;
-  align-items: center;
-  gap: 6px;
+  background: none;
+  border: none;
+  border-bottom: 2px solid transparent;
   cursor: pointer;
-  user-select: none;
-  border-bottom: 1px solid var(--border);
+  transition: var(--transition);
+  text-align: center;
+  font-family: var(--font);
 }
-.doc-outline__toggle {
-  font-size: 9px;
-  color: var(--text-2);
-}
-.doc-outline__count {
+.sidebar-tabs__tab:hover {
+  color: var(--text);
   background: var(--bg-hover);
-  color: var(--text-2);
-  font-size: 10px;
-  padding: 0 6px;
-  border-radius: 8px;
-  line-height: 16px;
 }
-.doc-outline__item {
-  padding: 4px 10px;
-  font-size: 12px;
+.sidebar-tabs__tab--active {
+  color: var(--text);
+  border-bottom-color: var(--accent);
+}
+.sidebar-tabs__tab--disabled {
+  color: var(--text-3);
+  cursor: default;
+  opacity: 0.5;
+}
+.sidebar-tabs__tab--disabled:hover {
+  background: none;
+  color: var(--text-3);
+}
+
+/* ── Sidebar Outline ─────────────────────── */
+.sidebar-outline {
+  flex: 1;
+  overflow-y: auto;
+  padding: 8px 0;
+}
+.sidebar-outline__empty {
+  padding: 40px 16px;
+  text-align: center;
+  color: var(--text-3);
+  font-size: 13px;
+}
+.sidebar-outline__item {
+  padding: 5px 12px;
+  font-size: 13px;
   color: var(--text-2);
   cursor: pointer;
   white-space: nowrap;
   overflow: hidden;
   text-overflow: ellipsis;
   transition: var(--transition);
+  border-radius: var(--radius);
+  margin: 1px 6px;
 }
-.doc-outline__item:hover {
+.sidebar-outline__item:hover {
   background: var(--bg-hover);
   color: var(--text);
 }
-.doc-outline__item--h1 { font-weight: 600; color: var(--text); }
-.doc-outline__item--h2 { font-weight: 500; }
+.sidebar-outline__item--active {
+  background: var(--bg-active);
+  color: var(--text);
+  font-weight: 500;
+}
+.sidebar-outline__item--h1 { font-weight: 600; color: var(--text); }
+.sidebar-outline__item--h2 { font-weight: 500; }
 
 /* ── Responsive ──────────────────────────── */
 @media (max-width: 700px) {
@@ -691,5 +713,4 @@
   .folder-tree { max-height: 30vh; }
   .notes-editor__body--split { grid-template-columns: 1fr; }
   .notes-editor__body--split .notes-preview { display: none; }
-  .doc-outline { display: none; }
 }