Summary

Add a markdown-only Table of Contents panel that works in both existing editor modes:

• BlockNote WYSIWYG mode
• CodeMirror source mode

The panel should live on the right side of the editor, support click-to-jump navigation, highlight the active heading while scrolling, and persist global TOC settings (visibility, width, and max heading level).

Scope

• Add TOC settings types, store, and persistence hook
• Extend existing BlockNote and CodeMirror hooks for heading extraction/navigation
• Add reusable TOC UI components
• Integrate TOC panel into both markdown editor modes
• Add focused tests for store, hooks, and TOC UI

Acceptance criteria summary

• TOC renders markdown headings with correct indentation and empty state
• Clicking a TOC item navigates correctly in both BlockNote and CodeMirror modes
• Active heading updates while scrolling in both modes
• Toolbar toggle shows/hides TOC for markdown files only
• TOC width is resizable and clamped consistently across modes
• TOC visibility, width, and max heading level persist across app restarts and mode switches

Reference

Tech spec: _bmad-output/implementation-artifacts/tech-spec-markdown-toc-panel.md