feat(copilot): subagents

[Sg312]

Summary

Adds subagents to the copilot. Also adds components to see copilot plan, edit diffs in chat, and options. Adds nicer thinking text Makes diff view accept/reject optimistic Fixes chat load on refresh

Type of Change

• [x] New feature
• [x] Bug fix

Testing

Manual with @emir-karabeg

Checklist

• [x] Code follows project style guidelines
• [x] Self-reviewed my changes
• [x] Tests added/updated and passing
• [x] No new warnings introduced
• [x] I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)