Add multi-window support: notes can be opened in dedicated secondary
Tauri windows with editor-only layout (no sidebar, no note list).
Triggers: Cmd+Shift+Click on notes, Cmd+K → "Open in New Window",
Cmd+Shift+O shortcut, Note → "Open in New Window" menu bar item.
Secondary windows have their own auto-save, theme, and wikilink
navigation. Closing a secondary window does not affect the main window.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
