Feat v0.4.5 editor modes + document outline

Tri-state viewMode (rendered/edit/split) replaces binary preview toggle.
Split view uses CSS grid with synced scroll. Document outline panel parses
headings and supports click-to-scroll in both CM6 and preview. Mode
preference persisted to localStorage. Notes package bumped to v0.6.0.

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

CHANGELOG.md

@@ -2,6 +2,36 @@
 
 All notable changes to Switchboard Core are documented here.
 
+## v0.4.5 — Editor Modes + Document Outline
+
+### Added
+
+- **Tri-state view mode**: Notes open in rendered (read-only) mode by default.
+  Toolbar button cycles through Edit (CM6) and Split (side-by-side) modes.
+  Replaces the old binary preview toggle.
+- **Split view**: Side-by-side CM6 editor + rendered preview using CSS grid.
+  CM6 instance preserved when toggling between edit and split modes.
+- **Synced scroll**: In split mode, scrolling the CM6 editor proportionally
+  scrolls the preview pane via linear ratio mapping on `scrollDOM`.
+- **View mode persistence**: User's preferred mode saved to localStorage
+  (`sw.storage.local('notes')`). New `editor_mode` manifest setting with
+  admin-level default (rendered / edit / split).
+- **Document outline**: Collapsible TOC panel adjacent to the editor body.
+  `parseHeadings()` extracts heading level, text, and line number (skips
+  fenced code blocks). Click heading to scroll — uses CM6
+  `EditorView.scrollIntoView()` in edit/split mode, DOM `scrollIntoView()`
+  in rendered mode. Updates on body change with 300ms debounce.
+
+### Changed
+
+- Notes package version bumped from 0.5.0 to 0.6.0.
+- Editor body wrapped in `.notes-editor__content` flex container to
+  accommodate the outline panel.
+- Wikilink click handling active in both rendered and split modes.
+- Mobile: split view collapses to single column, outline panel hidden.
+
+---
+
 ## v0.4.4 — Rich Editor + Import/Export
 
 ### Added