Add rich editor toolbar and context menu

[beNative]

Summary

• add a rich text toolbar plugin that exposes over fifteen authoring actions, updates selection state, and synchronizes with the editor engine
• add a contextual menu for the rich editor that mirrors the toolbar actions and closes automatically on scroll or escape
• keep existing Lexical integration intact while sharing toolbar actions with the parent editor component for Monaco parity controls

Testing

• npm run test:markdown

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Codex Task