feat(annotator): annotation notes as rewrite guidance

[coderdevin]

Summary

• MODIFY, ADD, and DELETE annotations now treat user notes as direction/suggestions for the LLM rather than literal replacements
• DELETE now opens a popover for user input instead of committing immediately
• Updated export prompt instructions to reflect guidance-based workflow

Test plan

• Open annotator, select text, press M — verify placeholder says "How should this be improved?"
• Select text, press D — verify popover opens with "Why or how should this be removed?"
• Click "Copy All" — verify exported markdown uses new labels and instructions

🤖 Generated with Claude Code