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/manifest.json

@@ -6,9 +6,9 @@
   "route": "/s/notes",
   "auth": "authenticated",
   "layout": "single",
-  "version": "0.6.0",
+  "version": "0.7.0",
   "icon": "📝",
-  "description": "Markdown notes surface with rich editor, folders, tags, backlinks, import/export, and document outline.",
+  "description": "Markdown notes surface with rich editor, folders, tags, backlinks, import/export, sidebar tabs, and document outline.",
   "author": "switchboard",
 
   "permissions": ["db.write"],